Methods and systems for detecting impairment of a lambda probe due to outgassing sealant

Abstract

Procedure, comprehensive: in response to a change in the demand for fuel supply to an engine without a change in the engine power demand at an engine exhaust temperature greater than a threshold temperature, indicating impairment of a lambda sensor connected to an engine exhaust system by a sealant, due to outgassing sealant; and Correcting lambda sensor measurements in response to the input.

Description

AREA

[0001] The following description generally concerns lambda sensors of an internal combustion engine. BACKGROUND / SUMMARY

[0002] A lambda sensor, such as a wideband lambda (universal exhaust gas oxygen - UEGO) sensor, can be positioned in a vehicle's exhaust system to detect the air-fuel ratio (AIRV) of the exhaust gas from the vehicle's internal combustion engine. The lambda sensor readings can be used to adjust the engine's operation, for example, by changing the amount of fuel injected to achieve a target AIV. Therefore, a malfunctioning lambda sensor can impair fuel injection control, potentially leading to increased emissions, reduced vehicle drivability, and decreased fuel efficiency.

[0003] The design and function of an oxygen sensor are described in NN: Operating Principle and Construction of Zirconium Dioxide Oxygen Sensors. SST Sensing Ltd, 2010. Pages 1 and 11.

[0004] US 7,197,912 B1 describes a gas sensor seal and a method for manufacturing one. The seal may consist of, among other things, a silicone-containing material.

[0005] Lambda sensors are often installed using a sealant, such as silicone sealant. However, exhaust gas can reach a temperature hot enough to cause the sealant to release gases—a phenomenon known as outgassing. Outgassing sealant can impair the lambda sensor by interfering with oxygen concentration measurements. Unlike general impairment due to, for example, sensor aging, impairment from outgassing sealant can occur rapidly.

[0006] Other approaches that address the impairment of a lambda sensor due to outgassing sealant involve applying a bias voltage to adjust the lambda sensor's measurement output. An exemplary approach is presented by Zarkhin et al. in US 6,382,013 B1. In this approach, impairment due to outgassing sealant is detected by a reversal of the measurement output (e.g., from positive volts to negative volts), and the measurement output is adjusted using a predetermined bias voltage applied to a sensor return lead. The inventors note that the absolute value of the sensor measurement remains correct despite the reversal.

[0007] However, the inventors of the present invention have recognized potential problems with such methods. For example, outgassing sealant can cause the lambda sensor to measure rich (e.g., because the released gases dilute the oxygen concentration in the exhaust gas) or lean (e.g., because sealant gases coat the sensor). Therefore, the effects of an outgassing sealant can be more complex than simply reversing the output voltage of the lambda sensor.

[0008] The aforementioned problems are solved by the features of the independent patent claims; advantageous further developments of the invention are the subject of the dependent claims.

[0009] In one example, the problems described above can be solved by a procedure comprising, in response to a change in the fuel supply demand to an engine without a change in the engine power demand at an engine exhaust temperature greater than a threshold temperature, indicating impairment of a lambda sensor connected to the engine's exhaust system by a sealant due to outgassing sealant; and correcting lambda sensor measurements in response to the indication. In this way, impairment of a lambda sensor by outgassing sealant can be detected and the lambda sensor measurements can be compensated for.

[0010] As an example, indicating impairment of the lambda sensor due to outgassing sealant further includes indicating impairment of the lambda sensor due to outgassing sealant without a sensor coating when the lambda sensor measures a rich air-fuel ratio in the engine exhaust in conjunction with reduced fuel consumption, and indicating impairment of the lambda sensor due to outgassing sealant with a sensor coating when the lambda sensor measures a lean air-fuel ratio in the engine exhaust in conjunction with increased fuel consumption. In this way, impairment due to outgassing sealant without a sensor coating can be distinguished from impairment caused by the lambda sensor being coated with sealant gases.Although oxygen measurements taken by a lambda sensor affected by outgassing sealant without a sensor coating can be corrected in the same way as oxygen measurements taken by a lambda sensor affected by outgassing sealant with a sensor coating, damage to the lambda sensor due to outgassing sealant with a sensor coating can be irreversible. Therefore, it is advantageous to differentiate between the two forms of damage due to outgassing sealant (e.g., with and without a sensor coating) to determine when a sensor replacement is indicated. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 shows a schematic representation of a vehicle's engine system. Fig. Figure 2 shows a schematic representation of an example lambda sensor. Fig. Figure 3 shows a block diagram illustrating an exemplary control architecture for generating a fuel command. Fig. Figure 4 shows a higher-level flowchart illustrating an exemplary procedure for detecting impairment of a UEGO probe due to outgassing sealant. Fig. Figure 5 shows an exemplary method for detecting impairment of fuel injection devices. Fig. Figure 6 shows an exemplary method for detecting impairment of a MAF sensor. Fig. Figure 7 shows an exemplary procedure for detecting impairment behavior of a UEGO probe of the delay type and slow-reacting type. Fig. Figure 8 shows a flowchart illustrating an exemplary procedure for correcting a UEGO probe measurement in response to a report of impairment of a UEGO probe due to outgassing sealant. Fig. Figure 9 shows an exemplary time sequence for detecting impairment of a UEGO probe due to outgassing sealant and applying a correction to an oxygen measurement. DETAILED DESCRIPTION

[0011] The following description concerns systems and methods for determining the impairment of a lambda sensor due to outgassing sealant in a vehicle's engine system and applying a correction to the sensor measurement. As in Fig. As shown in Figure 1, the engine system can include a lambda sensor located upstream of an emission control device. This upstream lambda sensor can be a UEGO sensor, such as the one shown in Figure 1. Fig. Figure 2 shows an exemplary UEGO sensor, designed to measure the amount of oxygen in the exhaust gas. Engine operation can be controlled based on feedback from the UEGO sensor, as shown in Figure 2. Fig. Figure 3 shows that the probe must be controlled to achieve a target LKV (lower flow rate). Outgassing sealant can impair the UEGO probe, causing it to incorrectly measure rich (due to hydrocarbons released from the sealant) or lean (due to the probe becoming coated with sealant), as shown in the exemplary procedure from [reference missing]. Fig. 4 can be determined. As part of determining whether a lambda sensor is impaired due to outgassing sealant, impairment of fuel injection devices and impairment of a MAF sensor can be determined according to the exemplary methods from the Fig. 5 or 6 must be excluded beforehand. Furthermore, impairment of a lambda sensor due to outgassing sealant leads to a different impairment behavior than impairment of a lambda sensor due to factors such as aging, which can be demonstrated using the exemplary procedure from Fig. 7 can be determined. A measurement correction can be made in response to a report of impairment of a lambda probe due to outgassing sealant, according to the exemplary procedure from Fig. 8 learned and applied. Fig. Figure 9 shows an exemplary time sequence for diagnosing impairment of a lambda probe due to outgassing sealant (with and without probe coating) and applying the measurement correction.

[0012] Fig. Figure 1 illustrates a schematic representation showing a cylinder of a multi-cylinder engine 10, which may be contained in an engine system 1. The engine system 1 may be a drive system contained in a motor vehicle 5. The engine 10 may be controlled, at least partially, by a control system including a controller 12 and by inputs from a driver 132 via an input device 130. In this example, the input device 130 includes an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. A combustion chamber (e.g., a cylinder) 30 of the engine 10 may have combustion chamber walls 32 with a piston 36 positioned therein. The piston 36 may be coupled to the crankshaft 40, so that an alternating motion of the piston is translated into a rotational motion of the crankshaft.The crankshaft 40 can be coupled to at least one drive wheel of a vehicle via an intermediate gear system. Furthermore, a starter motor can be coupled to the crankshaft 40 via a flywheel to enable the engine 10 to be started.

[0013] The combustion chamber 30 can draw in intake air from an intake manifold 44 via an intake port 42 and expel combustion gases via an exhaust port 48. The intake manifold 44 and the exhaust port 48 can be selectively connected to the combustion chamber 30 via a corresponding intake valve 52 and exhaust valve 54. In some embodiments, the combustion chamber 30 can include two or more intake valves and / or two or more exhaust valves. In this example, the inlet valve 52 and exhaust valve 54 can be controlled by cam actuation via one or more cams and can use one or more of cam profile switching (CPS), variable cam timing (VCT), variable valve timing (VVT) and / or variable valve lift (VVL) systems, which can be operated by the controller 12, to vary the valve operation.The position of the inlet valve 52 and exhaust valve 54 can be determined by position sensors 55 and 57, respectively. In alternative embodiments, the inlet valve 52 and / or the exhaust valve 54 can be controlled by electric valve actuation. For example, the cylinder 30 can alternatively include an inlet valve controlled by electric valve actuation and an exhaust valve controlled by cam actuation, including CPS and / or VCT systems.

[0014] In some embodiments, each cylinder of the engine 10 can be equipped with one or more fuel injection devices to supply it with fuel. As a non-limiting example, cylinder 30 is shown to include a fuel injection device 66, which is supplied with fuel from the fuel system 172. According to the illustration, the fuel injection device 66 is directly coupled to cylinder 30 to inject fuel directly into it in proportion to the pulse width of the FPW signal received by the controller 12 via an electronic driver 68. In this way, the fuel injection device 66 provides so-called direct injection (hereinafter also referred to as "DI") of fuel into the combustion cylinder 30.

[0015] It is understood that, in an alternative embodiment, the fuel injection device 66 can be an injection device with one nozzle per intake port, which supplies fuel to the intake port upstream of the cylinder 30. It is further understood that the cylinder 30 can receive fuel from a plurality of injection devices, such as a plurality of injection devices with one nozzle per intake port, a plurality of direct injection devices, or a combination thereof.

[0016] With further reference to Fig. 1. The intake port 42 can contain a throttle 62, which has a throttle valve 64. In this specific example, the position of the throttle valve 64 can be varied by the control unit 12 via a signal provided to an electric motor or actuator contained within the throttle 62, a design commonly referred to as electronic throttle control (ETC). In this way, the throttle 62 can be operated to vary the intake air supplied to the combustion chamber 30, along with other engine cylinders, through the intake port 42 and the intake manifold 44. The position of the throttle valve 64 can be provided to the control unit 12 by the throttle position signal TP.The intake duct 42 can include a sensor 120 for mass air flow (MAF) and a sensor 122 for manifold air pressure (MAP) to provide the control 12 with the appropriate MAF and MAP signals.

[0017] An ignition system 88 can provide a spark to the combustion chamber 30 via a spark plug 92 in response to a pre-ignition signal SA from the control unit 12 under selected operating modes. Although spark ignition components are shown, in some embodiments the combustion chamber 30 or one or more other combustion chambers of the engine 10 can be operated in a compression ignition mode with or without a spark.

[0018] According to the illustration, an upstream exhaust gas sensor 126 is coupled to the exhaust gas channel 48 upstream of the emission control device 70. The upstream sensor 126 can be any suitable sensor for providing an indication of the exhaust gas flow rate, such as a linear wideband lambda sensor or UEGO; a narrowband dual-state lambda sensor or EGO; a heated EGO (HEGO); or a NO x -, HC, or CO probe. In the non-restrictive embodiments described here, the upstream exhaust gas probe 126 is a UEGO probe designed to provide an output, such as a voltage signal, proportional to the amount of oxygen present in the exhaust gas. The controller 12 uses the output to determine the exhaust gas LKV.

[0019] In the illustration, the emission control device 70 is arranged downstream of the exhaust gas probe 126 along the exhaust gas channel 48. In the non-restrictive embodiments described here, the emission control device 70 is a three-way catalyst (TWC) designed to reduce NOₓ emissions. x to reduce and oxidize CO and unburned hydrocarbons. In other embodiments, however, the emission control device 70 may be a NO x -trap, various other emission control devices or combinations thereof.

[0020] A second downstream exhaust gas sensor 128 is shown coupled to the exhaust gas channel 48 downstream of the emission control device 70. The downstream sensor 128 can be any suitable sensor for providing an indication of the exhaust gas mixture, such as a UEGO sensor, an EGO sensor, a HEGO sensor, etc. For example, the downstream exhaust gas sensor 128 can be a HEGO sensor designed to indicate the relative enrichment or leaning of the exhaust gas after it has passed through the catalyst. Thus, the HEGO sensor can provide an output in the form of a switching point or a voltage signal at the point where the exhaust gas changes from lean to rich.

[0021] As in Fig. As shown in Figure 1, the engine system 1 can include an exhaust gas recirculation (EGR) system to direct a desired portion of the exhaust gas from the exhaust port 48 to the intake manifold 44 via the EGR channel 140. The amount of EGR supplied to the intake manifold 44 can be varied by the control unit 12 via an EGR valve 142. Furthermore, an EGR sensor 144 can be located within the EGR channel and provide information on one or more parameters, including the pressure, temperature, and oxygen concentration of the exhaust gas. Under certain conditions, the EGR system can be used to regulate the temperature of the air-fuel mixture within the combustion chamber.

[0022] Control 12 is in Fig. 1 is represented as a microcomputer, which includes a microprocessor unit 102, input / output ports 104, an electronic storage medium for executable programs and calibration values, which in this specific example is represented as a read-only memory chip 106, direct access memory 108, keep-alive memory 110 and a data bus.In addition to the signals discussed previously, the control unit 12 can receive various signals from sensors coupled to the engine 10, including the measurement of mass airflow (MAF) from a mass airflow sensor 120, engine coolant temperature (ECT) from a temperature sensor 112 coupled to a cooling sleeve 114, a profile ignition pickup (PIP) signal from a Hall effect sensor 118 (or other type) coupled to the crankshaft 40, a throttle position (TP) from a throttle position sensor, a manifold absolute pressure (MAP) signal from sensor 122, a UEGO sensor output (UEGO) from UEGO sensor 126, and a HEGO sensor output (HEGO) from HEGO sensor 128. An engine speed signal (RPM) can be generated by the control unit 12 from the PIP signal.

[0023] Computer-readable data, representing non-volatile instructions, can be programmed onto the read-only memory 106 of a storage medium. These instructions can be executed by the processor 102 to perform the procedures described below, as well as other variations that are anticipated but not explicitly listed.

[0024] As described above, shows Fig. 1 merely one cylinder of a multi-cylinder engine and each cylinder can equally contain its own set of inlet / exhaust valves, fuel injection(s), spark plug(s), etc.

[0025] Next, we will show Fig. Figure 2 shows a schematic view of an embodiment of a lambda sensor 200 designed to measure the concentration of oxygen (O2) in an intake air stream in an intake manifold or an exhaust gas stream in an exhaust manifold of an engine. The sensor 200 can be, for example, a UEGO sensor 126 made of Fig. 1. The probe 200 comprises a plurality of layers of one or more ceramic materials arranged in a stacked configuration. In the embodiment consisting of Fig. Figure 2 shows five ceramic layers, designated as layers 201, 202, 203, 204, and 205. These layers comprise one or more layers of a solid electrolyte capable of conducting oxygen ions. Examples of suitable solid electrolytes include zirconia-based materials. In some embodiments, a heating device 207 may also be arranged in thermal contact with the layers to increase their ionic conductivity. While the illustrated lambda probe is formed from five ceramic layers, it is understood that the lambda probe may include other suitable numbers of ceramic layers.

[0026] Layer 202 comprises a material or materials that create a diffusion path 210. The diffusion path 210 can be designed to allow one or more components of intake air or exhaust gas, including, among others, a desired analyte (e.g., O2), to diffuse into a first inner cavity 222 at a more limiting rate than the rate at which the analyte can be pumped in or out through a pair of pump electrodes 212 and 214. In this way, a stoichiometric amount of O2 can be obtained in the first inner cavity 222.

[0027] The probe 200 further includes a second inner cavity 224 within layer 204, which is separated from the first inner cavity 222 by layer 203. The second inner cavity 224 is designed to maintain a constant oxygen partial pressure corresponding to a stoichiometric state. An oxygen level (e.g., concentration) present in the second inner cavity 224 is equal to the oxygen level that the intake air or exhaust gas would have if the air-fuel ratio were stoichiometric. The oxygen concentration in the second inner cavity 224 is controlled by a pumping voltage V. cp kept constant. The second inner cavity 224 can be referred to here as the reference cell.

[0028] A pair of measuring electrodes 216 and 218 is arranged in communication with the first inner cavity 222 and the reference cell 224. The measuring electrodes 216 and 218 detect a concentration gradient that can develop between the first inner cavity 222 and the reference cell 224 due to an oxygen concentration in the intake air or exhaust gas that exceeds or falls below the stoichiometric amount. A high oxygen concentration can be caused by a lean intake air or exhaust gas mixture, while a low oxygen concentration can be caused by a rich mixture. As described here, outgassing sealant can also influence the concentration gradient measured by the measuring electrodes 216 and 218. For example, hydrocarbons released by the sealant can diffuse into the first inner cavity 222, diluting the oxygen concentration and causing the probe 200 to register a rich reading.In another example, the sealant can coat the probe 200, thereby blocking the diffusion path 210 and preventing gas components, such as O2, from escaping the first inner cavity 222, causing the probe 200 to measure lean. This can also result in a delayed response time of the probe 200. For example, if the exhaust gas transitions from a lean to a rich composition, the coating on the probe 200 can delay the diffusion of the lean exhaust gas from the first inner cavity 222 and the diffusion of the new, rich exhaust gas into the first inner cavity 222, causing the probe 200 to measure lean even when lean fuel conditions no longer exist.Conversely, when transitioning from a rich to a lean exhaust gas composition, the coating on the probe 200 can delay the diffusion of the rich exhaust gas from the first inner cavity 222 and the diffusion of the new, lean exhaust gas into the first inner cavity 222, causing the probe 200 to measure rich even when rich fuel conditions no longer exist.

[0029] In other examples, gas released by the sealant can react with components of the exhaust gas, altering its chemical composition. This can affect the exhaust gas composition in several ways, depending on the sealant's chemical composition. For instance, if the gas released by the sealant contains a halogen, such as chlorine (Cl) or bromine (Br), the intense heat of the exhaust gas can trigger a halogenation reaction. In this reaction, a hydrogen atom in a hydrocarbon already present in the exhaust gas due to combustion is replaced by the halogen. Because of the halogen's increased mass and size compared to the hydrogen, the diffusion rate of the halogenated hydrocarbon may be slower, resulting in a lean reading from the probe.In another example, if the gas released by the sealant is an oxidant, the oxidant can react with hydrocarbons in the exhaust gas and cause the probe to measure lean at 200.

[0030] The pair of pump electrodes 212 and 214 is arranged in communication with the first inner cavity 222 and is designed to electrochemically pump a selected gas component (e.g., O2) from the first inner cavity 222 through layer 201 and out of probe 200. Alternatively, the pair of pump electrodes 212 and 214 can be used to electrochemically pump a selected gas through layer 201 and into the inner cavity 222. The pump electrodes 212 and 214 can be referred to here as an O2 pump cell.

[0031] The electrodes 212, 214, 216, and 218 can be made of various suitable materials. In some embodiments, the electrodes 212, 214, 216, and 218 can be made at least partially of a material that catalyzes the splitting of molecular oxygen. Examples of such materials include platinum and silver.

[0032] The process of electrochemically pumping oxygen from or into the first inner cavity 222 involves applying a pumping voltage V p at the pump electrode pair 212 and 214. The pump voltage V p The flow applied to the O2 pump cell pumps oxygen into or out of the first inner cavity 222 to maintain a stoichiometric amount of oxygen therein. The resulting pump flow I p is proportional to the oxygen concentration in the exhaust gas. A control system (in Fig. 2 (not shown) generates the pump current signal I pdepending on the intensity of the applied pump voltage V p , which is required to maintain a stoichiometric amount within the first inner cavity 222. Thus, a lean mixture causes oxygen to be pumped out of the first inner cavity 222, and a rich mixture causes oxygen to be pumped into the first inner cavity 222.

[0033] It is understood that the lambda sensor described here is merely an exemplary embodiment of a lambda sensor and that other embodiments of lambda sensors may have additional and / or alternative features and / or designs.

[0034] The lambda sensor output (e.g., I p) can be used to adjust the engine's operation. For example, the amount of fuel supplied to the engine's cylinders can be varied using a forward-feedback approach (e.g., based on a desired engine torque, airflow through the engine, etc.) and / or feedback (e.g., using the lambda sensor output). Regarding Fig. Figure 3 illustrates a block diagram of a control architecture 300, which is implemented by a motor control, such as the control 12 from Fig. 1, can be implemented to generate a fuel command. The control architecture 300 includes a motor 327 and a UEGO probe 330 upstream of a TWC 335. For example, the motor 327 can be connected to the motor 10 from Fig. 1 corresponds to the UEGO probe 330 of the UEGO probe 126 from Fig. 1 correspond and the TWC 335 can be the emission control device 70 from Fig. 1 corresponds.

[0035] The control architecture 300 regulates the engine idle speed control (ISC) to a near-stoichiometric setpoint (e.g., a commanded ISC). The inner loop controller 307, comprising a proportional-integral differential (PID) controller, controls the engine ISC by generating a corresponding fuel command (e.g., fuel pulse width). A summing point 322 optionally combines the fuel command from the inner loop controller 307 with commands from a forward-coupled controller 320. This combined set of commands is transmitted to the fuel injection devices of the engine 327.

[0036] The UEGO sensor 330 provides a feedback signal to the internal loop controller 307. The UEGO feedback signal is proportional to the oxygen content of the engine exhaust gas between the engine 327 and the TWC 335. The output of the UEGO sensor 330 can be used, for example, to determine the discrepancy between a commanded (e.g., target) LKV (air mixture control) and an actual LKV, as detected by the UEGO sensor 330. Under nominal operating conditions of the UEGO sensor (e.g., an exhaust gas temperature higher than a minimum temperature required for UEGO operation and lower than a threshold temperature at which sealant outgasses), such a discrepancy can be attributed to fuel injection device and / or air metering errors, e.g., due to a malfunction of the fuel injection devices or a malfunction of the MAF sensor.

[0037] An outer loop controller 305 generates a UEGO reference signal, which is provided to the inner loop controller 307. The UEGO reference signal corresponds to a UEGO output indicating the commanded LKV (fuel mixture control). The UEGO reference signal is combined with the UEGO feedback signal at the junction 316. The error or differential signal provided by the junction 316 is then used by the inner loop controller 307 to adjust the fuel command so that the actual LKV in the engine 327 is driven to the target LKV. The outer loop controller 305 can be a suitable controller that includes an integral element, such as a proportional-integral (PI) controller.

[0038] In this way, the engine control unit can precisely control the engine's idle speed control (ISCV) based on feedback from the UEGO sensor and adaptively learn fuel injection and / or air metering errors, which can then be compensated for by adjusting the fuel command until the engine's actual ISC reaches the target ISC. For example, if the UEGO sensor measures a rich mixture, the amount of fuel supplied is reduced. Conversely, if the UEGO sensor measures a lean mixture, the amount of fuel supplied is increased. However, interference with the UEGO sensor due to outgassing sealant can prevent the feedback from the UEGO sensor from reflecting the engine's actual ISC, thus impairing fuel control.

[0039] Fig. Figure 4 shows a higher-level flowchart illustrating an exemplary procedure for determining impairment of a UEGO probe due to outgassing sealant in an engine system (e.g., engine system 1). Fig. 1) illustrated, which is then achieved using a compensation algorithm (as in relation to Fig. 8 described) can be corrected. Furthermore, other sources of interference in the engine system that could obscure the determination of outgassing, such as interference with fuel injection devices and interference with a MAF sensor, can be ruled out. Instructions for carrying out procedure 400 and the other procedures contained herein can be issued by a controller (e.g., controller 12 from Fig. 1) based on instructions stored in a memory of the control unit and in conjunction with signals from sensors of the engine system, such as those mentioned above in relation to Fig. 1 described sensors (e.g. the UEGO probe 126 from Fig. 1) are received and executed. The controller can use motor actuators of the motor system to adjust the motor operation according to the procedures described below.

[0040] Procedure 400 begins at 402 and involves estimating and / or measuring engine operating conditions. Operating conditions can be estimated, measured, and / or derived from available data and may include a commanded LKV (low-speed power), exhaust gas temperature, engine speed and load, driver-requested torque level, fuel consumption, etc.

[0041] In procedure 404, procedure 400 may involve diagnosing one or more fuel injection devices, as described in relation to Fig. 5 described. For example, a faulty fuel injection system that supplies more fuel than commanded can cause the engine to run rich. Conversely, a faulty fuel injection system that supplies less fuel than commanded can cause the engine to run lean. Thus, it can be advantageous to rule out these possibilities to determine whether the UEGO sensor reading is rich or lean due to outgassing sealant, with or without the sensor coating, as described below.

[0042] In case 406, procedure 400 may include diagnosing a MAF sensor (e.g., the MAF sensor 120 from Fig. 1), as in relation to Fig. 6. If the MAF sensor, for example, indicates an airflow into the engine that is too high, the commanded fuel quantity may be greater than is appropriate for the actual airflow and the target air-fuel ratio (IVR), resulting in a rich engine mixture. Conversely, if the MAF sensor indicates an airflow into the engine that is too low, the commanded fuel quantity may be less than is appropriate for the actual airflow and the target IVR, resulting in a lean engine mixture. As with any impairment of fuel injection devices, it may be advantageous to rule out impairment of the MAF sensor in order to determine with a high degree of certainty whether impairment of the UEGO sensor is due to outgassing sealant and / or a coating.

[0043] As an alternative to diagnosing one or more fuel injectors at 404 and the MAF sensor at 406, the control unit can utilize adaptive learning of LKV offset values ​​caused by faulty fuel injectors or a faulty MAF sensor, as in relation to Fig. 3 described and further described in 412.

[0044] In procedure 408, procedure 400 involves determining whether entry conditions for diagnosing UEGO sensor impairment due to sealant outgassing are met. Entry conditions for diagnosing UEGO sensor impairment due to sealant outgassing include, for example, a constant driver-requested torque (or engine load) combined with a change in fuel demand (increased or decreased). Entry conditions for diagnosing UEGO sensor impairment due to sealant outgassing may also include the exhaust gas temperature being greater than a threshold temperature. The threshold may be such that temperatures above the threshold are hot enough to cause sealant outgassing. The exhaust gas temperature may be measured directly by an exhaust gas temperature sensor. Alternatively, the exhaust gas temperature may be estimated based on UEGO heating output.For example, a UEGO heater, such as the heater 207, can be used. Fig. 2. The system is operated using a closed-loop control strategy to maintain a constant UEGO temperature; as the exhaust gas temperature increases, the amount of power supplied to the UEGO heater decreases. In another example, entry conditions for diagnosing UEGO probe impairment due to outgassing sealant may include the UEGO heater output being below a threshold power. Entry conditions for diagnosing UEGO probe impairment may also include an indication that the UEGO probe was recently repaired or replaced (e.g., within a specified time period), or that other maintenance of exhaust system components has taken place.Furthermore, entry conditions for diagnosing a UEGO sensor malfunction may include information that the fuel injector(s) is / are not malfunctioning (as diagnosed in 404) and the MAF sensor is not malfunctioning (as diagnosed in 406), if adaptive learning of LKV offset values ​​is not applied. If adaptive learning of LKV offset values ​​is applied, fuel and / or air metering errors may already be accounted for.

[0045] If the entry conditions for diagnosing UEGO probe impairment due to outgassing sealant are not met, procedure 400 proceeds to 410 and involves testing the UEGO probe for delayed-type and slow-response impairment behavior, as described in relation to Fig. 7 described.

[0046] In procedure 400, 412 may involve determining an offset in a measured LKV due to fuel and air metering errors. During UEGO nominal operation (e.g., the exhaust gas temperature is higher than a minimum temperature required for UEGO operation and lower than the threshold temperature at which outgassing occurs, and no UEGO impairment is indicated), deviations between the commanded LKV and the measured LKV may be due to fuel or air metering errors, as described in relation to Fig. 3 described. These errors can be long-term, and thus the offset can be continuously applied to ensure correct fuel delivery. Learning the offset can be advantageous for LKV control if it is later determined that the UEGO sensor is faulty, as in relation to the Fig. 7 and Fig. 8 described. Furthermore, determining the offset can be used as an alternative to determining an impairment of the fuel injection device, as described in relation to Fig. 5 described, and determining an impairment of the MAF sensor, as in relation to Fig. The procedures described in section 6 are used. Following section 412, procedure 400 ends.

[0047] If entry conditions for diagnosing UEGO probe impairment due to outgassing sealant are met at 408, procedure 400 proceeds to 414 and involves determining the LKV based on a UEGO probe output. The LKV can be determined, for example, from a UEGO probe pump flow, as described in relation to Fig. 2 described.

[0048] In procedure 416, Procedure 400 includes determining whether the UEGO sensor is measuring rich. Determining that the UEGO sensor is measuring rich may involve determining that the UEGO sensor pump flow is below a first threshold quantity. If the UEGO sensor is measuring rich, Procedure 400 proceeds to 418 and involves indicating impairment of the UEGO sensor due to outgassing sealant without a sensor coating. For example, hydrocarbons released by outgassing sealant may cause the UEGO sensor to measure rich even when a rich fuel condition is not present. Because the UEGO sensor output is used as feedback to the LKV control, fuel demand may be reduced, resulting in less fuel being supplied than is required for the engine operating conditions (e.g., requested torque and requested engine speed), as described in relation to Fig. 3 described. Reporting an impairment of the UEGO probe due to outgassing sealant without a probe coating may involve logging the results at the control unit. However, because the outgassing may be temporary (e.g., occurring during high exhaust temperatures and as long as the sealant contains gases to release), a vehicle operator may not be notified. Following 418, procedure 400 transitions to 426 as described below.

[0049] If the UEGO probe does not measure rich, procedure 400 proceeds to 420 and involves determining whether the UEGO probe is measuring lean. Determining that the UEGO probe is measuring lean may involve verifying that the UEGO probe pump flow is above a second threshold quantity. If the UEGO probe does not measure lean, procedure 400 proceeds to 422 and involves indicating the absence of any impairment of the UEGO probe due to outgassing sealant. For example, if the UEGO probe measurement indicates a stoichiometric LKV (low combustion chamber value), there may be no outgassing sealant present, even if the exhaust gas temperature is higher than the threshold temperature. Following 422, procedure 400 ends.

[0050] If the probe reads lean, Procedure 400 transitions to 424 and involves specifying an impairment of the UEGO probe due to outgassing sealant with probe coating. For example, if the UEGO probe is coated with sealant that is released through outgassing, and this causes it to read lean even when there is no lean fuel condition, then the fuel demand increases, resulting in more fuel being supplied than is required for the engine operating conditions, as in relation to Fig. 3 described. This can lead to high exhaust gas temperatures. It is understood that outgassing occurs prior to probe coating, and thus it may have been previously reported that the UEGO probe is affected by outgassing sealant without probe coating (e.g., at 418 of Procedure 400). Reporting UEGO probe impairment due to outgassing sealant with probe coating may involve logging the results to the control unit and illuminating a Malfunction Indicator Lamp (MIL). Furthermore, reporting UEGO probe impairment due to outgassing sealant with probe coating may involve reporting the reason for the MIL, e.g., via a human-machine interface, to notify the vehicle operator of the probe coating problem.Therefore, damage to the UEGO probe due to outgassing sealant with a probe coating can be a more severe form of damage to the UEGO probe due to outgassing sealant than damage without a probe coating. Method 400 then transitions to 426.

[0051] At 426, the procedure includes 400 correcting the UEGO oxygen measurement, as in relation to Fig. As described in section 8. By correcting the UEGO oxygen measurement, the determined LKV will be correct and the fuel command will be set accordingly. Following section 426, procedure 400 ends.

[0052] In relation to Fig. 5 is an exemplary method 500 for diagnosing a condition of one or more fuel injection devices based on a variation of the rotational speed accelerations of an engine (e.g., engine 10 from Fig. 1) shown after fuel injection into each cylinder of the engine. For example, if an exhaust gas sensor (such as the UEGO sensor 126 from Fig. 1) If the mixture measures lean and continues to measure lean despite an increased fuel demand, the engine may not be receiving the requested amount of fuel (e.g., insufficient fuel supply), which may be due to a malfunction of the fuel injection system, particularly at exhaust gas temperatures below a threshold for sealant outgassing (as in relation to Fig. (described in section 4). If the UEGO sensor reads rich and continues to read rich despite a reduced fuel demand, this may also be due to the engine not receiving the requested amount of fuel (e.g., excessive fuel supply). Thus, procedure 500 can be used as part of procedure 400. Fig. 4 (e.g., at 404) can be performed so that a change in fuel demand without a change in engine power demand can be conclusively attributed to an impairment of the UEGO sensor due to outgassing sealant. In an alternative embodiment, adaptive learning of LKV offset values, as with regard to Fig. 3 and at 412 of Fig. 4 described, instead of determining an impairment of the fuel injection device.

[0053] Procedure 500 begins with 502 and involves injecting fuel into each cylinder over a single engine stroke. For example, each cylinder (e.g., cylinder 30 from Fig. 1) a fuel injection at its time in a known firing order via a corresponding fuel injection device (e.g. the fuel injection device 66 from Fig. 1) received. As a result, each fuel injector can deliver fuel once in the single engine stroke.

[0054] In procedure 504, method 500 involves determining individual engine speed accelerations based on the injection of fuel into each cylinder and the combustion of the air-fuel mixture. The engine speed can increase proportionally to the amount of fuel injected (e.g., accelerate). A control unit (e.g., control unit 12 from Fig. 1) Can an engine speed signal be obtained from an engine speed sensor (such as the Hall effect sensor 118)? Fig. 1) During the injection event, the control unit receives and relates each engine speed acceleration (e.g., each position in the engine speed) to each fuel injector / cylinder based on the known firing order of the cylinders. As a result, the control unit can perform a logical determination of the individual engine speed accelerations for each fuel injector / cylinder based on logical rules that depend on the received (e.g., measured) engine speed signal and the known firing order.

[0055] In 506, the procedure involves comparing the individual engine speed acceleration values ​​for each fuel injector / cylinder and determining the variation in engine speed accelerations between the cylinders. In one example, the same amount of fuel may be injected into each cylinder via each corresponding fuel injector in 502. In another example, different amounts of fuel may be injected into each cylinder (e.g., due to variations in aging, wear, or impairment of the performance or characteristics of the fuel injectors). In both examples, however, approximately the same engine speed acceleration response is to be expected, since the amount of fuel requested for injection is the same for each cylinder.Therefore, in an example, determining the variation of engine speed accelerations between the cylinders may involve the control system calculating a standard deviation between the determined individual engine speed accelerations for each cylinder.

[0056] In 508, the procedure 500 involves determining whether the variation determined in 506 is greater than a predetermined threshold. In an example, the predetermined threshold may be a value indicating a change in the performance or impairment of one or more of the fuel injectors relative to the other fuel injectors, since a small degree of variation (e.g., within 1.5%) may be permissible between multiple injection events of the same fuel injector or between fuel injectors.

[0057] If the specified variation is not greater than the threshold, procedure 500 continues with 510 and involves indicating the absence of any impairment of fuel injectors. At 512, procedure 500 involves further fuel injection based on engine operating parameters (e.g., LKV, engine load, etc.). Alternatively, at 508, if the variation is greater than the threshold, procedure 500 continues with 514 and involves indicating impairment of one or more of the fuel injectors and determining which fuel injector (or injectors) is impaired, based on the individual engine speed accelerations and the known firing order of the engine cylinders. For example, the control unit may be informed of the position (e.g.,The crankshaft angle at which each individual engine speed acceleration occurred (based on an output from a crankshaft position or speed sensor) must be known. By comparing this with the known firing order and a known crankshaft angle at which each cylinder's fuel injector fires, the control unit can determine which individual engine speed acceleration belongs to each cylinder (and the corresponding fuel injector). The control unit can then determine which engine speed acceleration deviated from the other engine speed accelerations (or an average of all engine speed accelerations) and then indicate a detriment to the corresponding fuel injector (e.g., the fuel injector that injected fuel corresponding to an engine speed acceleration that deviated from the average by a threshold amount).

[0058] In procedure 516, procedure 500 involves determining whether the observed engine speed acceleration due to injection via the specified fuel injection device is greater than an expected engine speed acceleration. In one example, the expected engine speed acceleration could be the average engine speed acceleration of all engine cylinders. In another example, the expected engine speed acceleration could be determined using a lookup table with the commanded fuel injection quantity (or pulse width) as input and the expected engine speed acceleration as output.If the engine speed acceleration of the specified fuel injector is greater than the expected engine speed acceleration, procedure 500 continues with 518 and involves indicating an injection fault and / or an increase in the size of one or more nozzle holes of the injector because more fuel may have been injected by the specified fuel injector than intended. In an example, indicating an injection fault and / or an increase in the size of one or more nozzle holes of the injector may involve illuminating a MIL and may further include indicating the reason for the MIL (e.g., for service or replacement of the specified fuel injector). Following 518, procedure 500 ends.

[0059] If the engine speed acceleration of the specified fuel injector is not greater than the expected engine speed acceleration (e.g., less than it), Method 500 transitions to 520 and involves indicating one or more causes of a clogged fuel injector, mechanical impairment of the fuel injector, and impairment of a fuel injector solenoid. For example, less fuel may have been supplied by the specified fuel injector than intended. In one example, indicating a clogged fuel injector, mechanical impairment of the fuel injector, and / or impairment of a fuel injector solenoid may involve the illumination of a MIL and may further include indicating the reason for the MIL. Method 500 ends after 520.

[0060] Fig. Figure 6 shows an exemplary procedure 600 for diagnosing an air mass flow sensor (such as the MAF sensor 120 from Fig. 1), which is positioned so that it is connected to a motor (e.g., motor 10 from Fig. 1) in a vehicle (e.g. vehicle 5 from Fig. 1) measures the amount of incoming air. Method 600 can be implemented by means of a controller stored in memory, such as controller 12. Fig. 1. Stored instructions are executed to determine whether the amount of air entering the engine, as indicated by the MAF sensor, is correct. For example, a MAF sensor indicating an airflow into the engine that is too low or too high will cause the engine to run rich or lean, respectively, thus interfering with the diagnosis of UEGO sensor malfunction due to outgassing sealant (with or without subsequent sensor coating). Thus, Procedure 600 can be performed as part of Procedure 400 from Fig. 4 (e.g., at 406) can be performed so that a change in fuel demand without a change in engine power demand can be conclusively attributed to an impairment of the UEGO sensor due to outgassing sealant. In an alternative embodiment, adaptive learning of LKV offset values, as with regard to Fig. 3 and at 412 of Fig. 4 described, instead of determining an impairment of the MAF sensor.

[0061] Procedure 600 begins with 602 and involves estimating and / or measuring engine operating conditions. Engine operating parameters may include engine speed and load, atmospheric pressure, MAP and MAF, engine and / or manifold temperature, throttle position, driver-requested torque, etc. Operating conditions may be measured or inferred from available data.

[0062] In procedure 604, method 600 involves measuring an airflow (MAF1) using the MAF sensor. For example, the raw MAF sensor output can be converted into an airflow value using a MAF transfer function.

[0063] In the case of 606, the procedure involves 600 estimating an airflow (MAF2) based on the engine operating parameters. MAF2 can be determined, for example, at least partially by applying the engine speed (such as by a crankshaft position sensor, like the Hall effect sensor 118 from Fig. 1 measured), of the MAP (as measured by a manifold air pressure sensor, such as the MAP sensor 122 from Fig. The MAF2 calculation can be calculated using the measured values ​​(1) and the intake air temperature. Furthermore, the engine displacement and volumetric efficiency can be included as inputs. In another example, the throttle position (as measured by a throttle position sensor) can be included in the MAF2 calculation.

[0064] In procedure 608, the process involves calculating the absolute value of the difference between MAF1 and MAF2. This determines the difference between the measured airflow, MAF1, and the estimated airflow, MAF2.

[0065] In procedure 610, procedure 600 involves determining whether the absolute value of the difference between MAF1 and MAF2 is greater than a threshold. Using the absolute value, the magnitude of the difference, rather than its sign (positive or negative), is used to determine whether the difference is greater than the threshold. The threshold can be a predefined value set such that values ​​greater than the threshold indicate that MAF1 and MAF2 do not match.

[0066] If the absolute value of the difference between MAF1 and MAF2 is not greater than the threshold (e.g., the difference is less than or equal to the threshold), procedure 600 proceeds to 612 and involves stating the absence of any impairment of the MAF sensor. For example, measurements taken by the MAF sensor may be considered reliable for determining the amount of fuel to be supplied to the engine for a target air-fuel ratio. Procedure 600 ends after 612.

[0067] If the absolute value of the difference between MAF1 and MAF2 is greater than the threshold, procedure 600 transitions to 614 and involves indicating a malfunction of the MAF sensor. Indicating a malfunction of the MAF sensor may involve illuminating a MIL and may further involve informing a driver of the vehicle of the reason for the MIL. Furthermore, the control unit may estimate an airflow, as described in 606, and use the estimated airflow value (instead of the value measured by the malfunctioning MAF sensor) when determining the amount of fuel to supply to the engine for the target airflow ratio. Following 614, procedure 600 terminates.

[0068] Fig. Figure 7 shows an exemplary procedure 700 for diagnosing impairment of the UEGO probe, e.g., due to probe aging. The impairment behavior exhibited by a UEGO probe due to outgassing sealant (and subsequent probe coating) differs from general UEGO probe impairment; outgassing sealant can lead to rapid changes, whereas general impairment can result in gradual changes over time. For example, symmetrical and asymmetrical delays in the initial exhaust gas probe response, as well as symmetrical and asymmetrical slow responses during the transition from rich to lean and / or lean to rich exhaust gas, may indicate general UEGO probe impairment. These impairment response patterns can be referred to as the “six disturbance patterns.”Method 700 can help to distinguish a general impairment of the UEGO probe from an impairment due to outgassing sealant, and can be used as part of Method 400. Fig. Procedure 4 (as in 410) may be performed, for example, in response to the fact that entry conditions for diagnosing impairment of the UEGO probe due to outgassing sealant are not met. Furthermore, procedure 700 may be performed periodically (e.g., after a certain period since the procedure was last performed) to check for general impairment of the UEGO probe.

[0069] Procedure 700 begins with 702 and involves modulating the LKV by a motor (e.g., motor 10 from Fig. 1) of a vehicle (e.g. vehicle 5 from Fig. 1) exhaust gas through at least one cycle comprising a rich-to-lean transition and a lean-to-rich transition. Control commands can be issued by an engine control unit (e.g., control 12 from Fig. 1) or generated by a special control system and sent to the engine control unit to control fuel injection (e.g. the pulse width of the FPW signal sent to the driver 68 from Fig. 1 is sent) to adjust the amount of fuel entering the cylinders of the engine and / or one or more from a valve operation (e.g., the intake valve 52 from Fig. 1) and a throttle operation (e.g. the throttle 62 from Fig. 1) to adjust in order to control the air entering the engine's cylinders. In one example, the commanded LKV modulation is an intrusive lambda square wave. The LKV can be modulated by enough rich-to-lean and lean-to-rich transitions to obtain reaction time statistics. For example, the LKV can be modulated by six rich-to-lean and lean-to-rich cycles to obtain a suitable amount of data to perform a degradation assessment.

[0070] In some embodiments, the air-fuel ratio can be modulated during the transition into (entering) or out of (exiting) a deceleration fuel shut-off (DFSO) state. The vehicle can enter DFSO in response to a driver pedal position (e.g., in response to the driver releasing the pedal) and when the vehicle deceleration exceeds a threshold. By utilizing LKV modulation during DFSO, intrusive LKV modulation can be reduced, thereby decreasing or eliminating negative effects on emissions and vehicle handling.

[0071] It should be noted that during LKV modulation between rich and lean, if the driver requests a change in engine operating conditions (e.g. based on pedal position), the modulation may be suspended until the operating conditions are again suitable for determining an impairment of the UEGO sensor.

[0072] In procedure 704, procedure 700 involves determining an expected response time of the UEGO sensor (e.g., an expected time the UEGO sensor needs to respond to the commanded LKV change). The expected response time can be the sum of a duration (delay time) from the commanded LKV change until the initial sensor response and a weighted rate of increase for changing the sensor output by a calibrated amount to change the commanded LKV. The delay time between the commanded LKV change and the initial UEGO sensor response can be determined from several delay sources. First, there is a delay component from the time of fuel injection to the time of exhaust, which is inversely proportional to the engine speed.Secondly, there is a delay component due to the time it takes for the exhaust gas to flow from the engine cylinders to the exhaust gas sensor, which can vary depending on the reverse velocity or mass airflow rate of gas in the exhaust duct. Finally, there are delay components caused by processing times, the filtering applied to the exhaust gas sensor signal, etc., which are nearly constant. The weighted rise time can be determined based on the exhaust gas velocity, which affects the rate at which the exhaust gas diffuses into the UEGO sensor (e.g., via the diffusion path 210 of sensor 200). Fig. 2) Furthermore, the ascent time can vary with the applied amount of the LKV step, with the ascent time increasing as the amount of the step increases.

[0073] In procedure 706, the process involves measuring the reaction time of the UEGO probe. For example, the measured delay time and the measured weighted rise time for the UEGO probe reaction are used to calculate the UEGO probe reaction time.

[0074] In procedure 708, method 700 involves determining the difference between the expected and measured reaction times. This difference can be determined by subtracting the expected reaction time for a nominal probe from the total reaction time. Differences between measured and expected reactions can be recorded and averaged over a series of fat-to-lean and lean-to-fat transition cycles to increase the reliability of the reaction time difference as a metric for determining impairment.

[0075] For 710, procedure 700 involves determining whether the mean lean-to-rich response time difference and the mean rich-to-lean response time difference are greater than a first calibrated threshold. Small variations around the response time difference of a nominal exhaust gas sensor may not affect emissions or drivability. As an example, the first threshold may be calibrated to approximately 200 milliseconds (ms), which may be the threshold at which asymmetric impairment may begin to affect engine control stability and impact emissions and drivability. If the mean lean-to-rich response time difference and the mean rich-to-lean response time difference are not greater than the first calibrated threshold, procedure 700 proceeds to 712 and involves reporting the absence of impairment of the UEGO sensor. Following 712, procedure 700 terminates.

[0076] If the mean lean-to-fat response time difference and the mean fat-to-lean response time difference are greater than the first calibrated threshold, Procedure 700 proceeds to 714 and involves determining whether the mean lean-to-fat response time difference or the mean fat-to-lean response time difference is greater than a second calibrated threshold (a delay threshold, e.g., 600 ms). If a response time in one direction (e.g., from lean to fat) or in both directions (e.g., lean to fat and fat to lean) is greater than the second calibrated threshold, Procedure 700 proceeds to 722 and involves indicating impairment of the UEGO probe. For example, a response time delay in one direction is an asymmetric delay, whereas a response time delay in both directions is a symmetric delay.Indicating a faulty UEGO sensor may involve setting a diagnostic trouble code (DTC) on the control unit and may also involve illuminating a malfunction indicator lamp (MIL) to inform a driver that they need to have the vehicle serviced to repair or replace the faulty UEGO sensor. Furthermore, indicating a faulty UEGO sensor may also involve switching to an open-loop control strategy that does not utilize feedback from the UEGO sensor. For example, the fuel quantity may be determined using a forward-feed control (e.g., the 320 forward-feed control). Fig. 3) can be determined. Furthermore, learned offset values ​​can be affected by fuel and / or air metering errors (such as in 412 of Fig. (4 learned) are used when generating the fuel command. Following 722, the procedure ends in 700.

[0077] Referring again to 714, if the mean lean-to-fat reaction time difference or the mean fat-to-lean reaction time difference is not greater than the second calibrated threshold, procedure 700 proceeds to 716. In 716, procedure 700 involves determining whether a ratio of the mean fat-to-lean reaction time difference and the mean lean-to-fat reaction time difference lies within a threshold range centered on one. If the ratio of the mean fat-to-lean reaction time difference and the mean lean-to-fat reaction time difference is equal to one, then the mean fat-to-lean reaction time difference and the mean lean-to-fat reaction time difference are equal. Therefore, the threshold range defines a region in which the reaction time differences are symmetrical (i.e., occur in both directions).A deviation from the threshold range corresponds to a reaction time difference that is greater in one direction than the other, e.g., when the UEGO sensor's reaction time is more delayed compared to the nominal sensor reaction time during the transition from lean to rich than during the transition from rich to lean. Symmetrical-type impairment has little effect on emissions and drivability unless it is associated with a large delay (e.g., reaction time differences are beyond the second calibrated threshold, as determined at 714). However, asymmetrical-type impairment can have a significant effect on emissions even if the delay is small, because the air-fuel ratio may be distorted. Thus, for intermediate values ​​of the mean reaction time difference (e.g.,The reaction time (which lies between the first calibrated threshold and the second calibrated threshold) determines how much asymmetry is present in each LKV modulation reaction cycle.

[0078] If the ratio of the mean fat-to-lean reaction time difference to the mean lean-to-fat reaction time difference is not within the threshold range, procedure 700 proceeds to 722 and involves reporting an impairment of the UEGO probe, as described above. If the ratio of the mean fat-to-lean reaction time difference to the mean lean-to-fat reaction time difference is within the threshold range, procedure 700 proceeds to 720 and involves reporting the absence of an impairment of the UEGO probe. Following 720, procedure 700 ends.

[0079] Method 700 allows a single response time parameter (consisting of both a delay time and a weighted rise time) to be used as a pass / fail metric to diagnose general impairment of a UEGO probe based on six different types of impairment behavior (e.g., symmetric delay, asymmetric fat-to-lean delay, asymmetric lean-to-fat delay, symmetric slow response, asymmetric slow fat-to-lean response, and asymmetric slow lean-to-fat response). Furthermore, all six different types of impairment behavior are distinct from the rapid change in UEGO probe response caused by outgassing sealant. It should be noted that a UEGO probe exhibiting any of the six interference patterns may also exhibit impairment due to outgassing sealant.

[0080] In relation to Fig. Figure 8 now shows a flowchart illustrating a procedure 800 for applying a measurement correction to a lambda sensor, such as the UEGO sensor 126. Fig. 1, in a motor system (e.g., motor system 1 from Fig. 1) illustrated. Method 800 can be implemented, for example, by a controller (e.g., controller 12 from Fig. 1) in response to a report of impairment of a UEGO probe due to outgassing sealant (with or without probe coating), as in relation to Fig. 4 described. Specifically, Procedure 800 can be performed to determine a pump current correction factor based on voltages applied to a pump cell of the probe during no-fuel conditions, and can be used to correct a pump current output of a UEGO probe affected by outgassing sealant. Furthermore, if the UEGO probe output cannot be corrected, Procedure 800 can provide an option for determining the exhaust gas flow rate without UEGO probe feedback.

[0081] Procedure 800 begins with 802 and involves estimating and / or measuring engine operating conditions. Engine operating conditions may include, for example, a commanded LKV (low-pressure fuel mixture), the amount of EGR (exhaust gas recirculation) entering the engine cylinders, and fuel delivery conditions.

[0082] In procedure 804, part 800 involves determining whether no-fuel conditions exist. No-fuel conditions include, for example, vehicle braking conditions and engine operating conditions where the fuel supply is interrupted, but the engine continues to rotate and at least one intake valve and one exhaust valve are operating; thus, air flows through one or more of the cylinders, but no fuel is injected into the cylinders. Under no-fuel conditions, combustion does not occur, and ambient air can move through the cylinder from the intake to the exhaust. This allows the UEGO probe to collect ambient air on which measurements, such as an ambient oxygen concentration measurement, can be performed.

[0083] As noted, conditions without fuel supply can include, for example, DFSO. The vehicle can enter DFSO in response to a driver pedal position (e.g., in response to the driver releasing the pedal) and when the vehicle braking exceeds a threshold. DFSO conditions can occur repeatedly during a driving cycle, and thus multiple ambient oxygen measurement readings can be generated during the driving cycle, such as for each DFSO event.

[0084] In relation to Fig. Procedure 8, if it is determined that no no-fuel conditions exist, proceeds to 800 and involves determining whether UEGO sensor impairment due to outgassing sealant is reported for a threshold duration. If no UEGO sensor impairment due to outgassing sealant is reported for the threshold duration (e.g., the impairment was reported for less than the threshold duration), procedure 800 reverts to 802. This allows the control unit to continue monitoring engine operating conditions until no-fuel conditions occur or the threshold duration expires.

[0085] If impairment of the UEGO probe due to outgassing sealant (with or without probe coating) is indicated for the threshold duration, procedure 800 transitions to 808 and involves determining the LKV in a forward-coupled mode based on an estimated cylinder air mass charge and fuel quantity without UEGO probe feedback. For example, the cylinder air mass charge can be based on an output from a MAF sensor (e.g., MAF sensor 120 from Fig. 1) can be determined and the fuel quantity can be determined based on the FPW signal. Furthermore, feedback from a second lambda sensor (e.g., the HEGO sensor 128) is possible. Fig. 1), which includes a catalyst (e.g., the emission control device 70) Fig. 1) downstream, can be used. In addition, learned offset values ​​can be used due to fuel and / or air metering errors (such as in 412 of Fig. (4 learned) can be used. Thus, determining the LKV in the forward-coupled manner may be more accurate than using the output of a UEGO sensor, which is known to be affected by outgassing sealant. This can be particularly advantageous if the UEGO sensor has been reading lean for an extended period due to sensor coating. However, this operation may adversely affect the vehicle's ability to meet emission requirements. Therefore, Procedure 800 returns to 808 and then to 802 to further examine the engine operating conditions.

[0086] When no-fuel conditions are present at 804, the procedure proceeds from 800 to 810 and involves applying an initial pump voltage (V1) to the oxygen pump cell of the exhaust gas probe and receiving an initial pump current (Ip1). The initial pump voltage can be high enough to pump oxygen from the cell, but low enough to prevent the splitting of oxygen-containing molecules, such as water (H2O) (e.g., V1 = 450 mV). Applying the initial voltage produces an output from the probe in the form of the initial pump current (Ip1), which, in a properly functioning lambda probe, indicates the amount of oxygen in the sample gas (e.g., ambient air under no-fuel conditions). The concentration of oxygen in the ambient air is a known value (e.g., 21%).

[0087] In 812, the procedure involves applying a second pump voltage (V2) to the probe's oxygen pump cell, which receives a second pump current (Ip2). The second voltage can be greater than the first voltage applied to the probe. In particular, the second voltage can be high enough to split H2O molecules into hydrogen and oxygen (e.g., V2 = 1.1 V). Applying the second voltage generates the second pump current (Ip2), which, in a properly functioning lambda probe, indicates the amount of oxygen and water in the sample gas. It is understood that the term "water" in "amount of oxygen and water," as used here, refers to the amount of oxygen from the split H2O molecules in the sample gas.

[0088] In case 814, the procedure includes determining the dry air oxygen value (Ip) in 800. dry ) based on Ip1 and Ip2. A controller (e.g., controller 12 from Fig. 1) Can Ip1 and Ip2 be combined into a function to calculate Ip? dry insert. IP dry can be calculated, for example, as: IP dry = (Ip2 × 0.4) + (Ip1 × 0.6). Thus, Ip is taken into account. dry Differences in oxygen concentration (e.g. deviations of 21%) of the ambient air, which may be due to differences in humidity.

[0089] In case 816, the procedure includes 800 determining a UEGO probe correction factor (O2). cf ) based on IP dry The UEGO probe correction factor is a factor that compensates for variability between parts of the probe as well as impairment due to outgassing sealant. In one example, the correction factor can be expressed as the ratio of a reference sensor output (e.g., a nominal oxygen value from a nominal UEGO probe) to Ip. dry be determined.

[0090] In case 818, the procedure 800 involves determining whether O2 cfis greater than a threshold value. The threshold value can define a correction factor above which the UEGO probe is assumed to be severely impaired and the correction factor is unable to satisfactorily correct UEGO probe measurements. If O2 cf If the value exceeds the threshold, procedure 800 transitions to 820 and includes a recommendation to replace the UEGO probe. Furthermore, the control unit can determine the LKV in forward-coupled mode, as described in 808, until the probe is replaced. Procedure 800 ends after 820.

[0091] If O2 cf is not greater than the threshold (e.g., O2) cf (less than or equal to the threshold value), the procedure 800 transitions to 822 and involves correcting the UEGO probe measurements using O2 cf For example, an oxygen measurement can be performed by the UEGO probe using O2. cfThe values ​​are multiplied to produce a corrected oxygen measurement (e.g., the amount of oxygen that would be measured by a Nenne UEGO probe). Furthermore, if the LKV is determined in forward-coupled mode, the control can be switched back to using the UEGO probe output to determine the LKV. Procedure 800 ends after 822.

[0092] A correction factor can be determined based on sensor outputs (e.g., pump currents) generated in response to voltages applied to the UEGO sensor's oxygen pump cell under no-fuel conditions, and a reference sensor output. Applying this correction factor to the UEGO sensor reading during fuel-supplied conditions allows for the determination of an accurate oxygen concentration and, consequently, an accurate LKV (Liquid Combustion Value), even when the UEGO sensor reading is affected by outgassing sealant. The correction factor can be updated during any no-fuel condition, as the effect of outgassing sealant can change over time.Furthermore, incorrect engine operation can be avoided by disabling the use of the UEGO probe output to determine the LKV if there is a time delay between determining that the UEGO probe is affected by outgassing sealant and determining the correction factor (e.g., due to the absence of no-fuel conditions).

[0093] Fig. Figure 9 shows a diagram 900 illustrating an example of diagnosing UEGO sensor impairment due to outgassing sealant and coating in an engine system. UEGO sensor impairment due to outgassing sealant and coating can be determined in response to a change in fuel demand in the absence of a change in driver-requested torque at high exhaust temperatures (e.g., according to the procedure from [reference]). Fig. 4) The torque requirement is shown in curve 902, the exhaust gas temperature is shown in curve 904, the fuel consumption is shown in curve 908, the pump current of the UEGO sensor is shown in curve 910, an indication of an impairment of the UEGO sensor is shown in curve 916, an indication of an impairment of fuel injection devices is shown in curve 918, an indication of an impairment of the MAF sensor is shown in curve 920, and an application of a measured value correction of the UEGO sensor is shown in curve 922.Furthermore, a threshold exhaust gas temperature is indicated by a dashed line 906, a pump current of the UEGO sensor equal to stoichiometry is indicated by a dashed line 912 (below this line the sensor indicates rich fuel conditions and above it, it indicates lean fuel conditions), a first pump current threshold for the UEGO sensor (for indicating rich fuel conditions) is indicated by a dashed line 914a, and a second pump current threshold for the UEGO sensor (for indicating lean fuel conditions) is indicated by a dashed line 914b. In all of the above, the x-axis represents time, with time increasing from left to right.The y-axis refers to the specified parameter, with values ​​increasing from bottom to top, except for curve 916, which indicates the type of UEGO sensor impairment (or "Off" if no UEGO sensor impairment is indicated); curve 918, which indicates fuel injector impairment as "Off" or "On"; curve 920, which indicates MAF sensor impairment as "Off" or "On"; and curve 922, which indicates UEGO sensor measurement correction as "Off" or "On".

[0094] Starting from time t0, the engine is operated with a constant torque requested by the driver, as shown by curve 902. Due to the constant torque requirement, fuel consumption is also constant (curve 908), and the engine operates with a stoichiometric fuel consumption, as indicated by the fact that the pump current of the UEGO sensor (curve 910) is equal to the stoichiometric pump current (dashed line 912). No impairment of the UEGO sensor is indicated (curve 916), and therefore the UEGO sensor measurement correction is not applied (curve 922). Furthermore, no impairment of fuel injection devices (such as with the method from [reference missing]) is indicated. Fig. 5 diagnosed) indicated (course 918) and furthermore no impairment of the MAF sensor (such as with the procedure from Fig. 6 diagnosed) indicated (curve 920). However, between time t0 and time t1, the exhaust gas temperature rises, as shown by curve 904, and exceeds the threshold exhaust gas temperature (dashed line 906), which defines a temperature above which outgassing of sealant can occur. Thus, in the example of Fig. 9, where the exhaust gas temperature is above the threshold temperature, gases are released from the sealant used in the installation of the UEGO probe.

[0095] After time t1, the pump current of the UEGO sensor (curve 910) drops below stoichiometry (dashed line 912). Since the UEGO sensor output is used as feedback to generate the fuel command, fuel consumption (curve 908) also decreases, although the torque requirement (curve 902) remains constant. Even with decreasing fuel consumption, the pump current of the UEGO sensor continues to increase because increasing amounts of hydrocarbons are released from the sealant, further diluting the oxygen concentration in the exhaust gas.At time t2, in response to the fact that the pump current of the UEGO probe (curve 910) falls below the first pump current threshold for the UEGO probe to indicate rich fuel conditions (dashed line 914a), in combination with the constant torque requirement (curve 902), reduced fuel supply (curve 908), the exhaust gas temperature (curve 904) which is greater than the threshold exhaust gas temperature (dashed line 906), no indication of impairment of fuel injection devices (curve 918) and no indication of impairment of the MAF sensor (curve 920), an impairment of the UEGO probe due to outgassing sealant without probe coating is indicated (curve 916).

[0096] Between time t2 and time t3, the UEGO sensor pump current (curve 910) continues to decrease until it reaches a minimum. Fuel consumption (curve 908) decreases accordingly, although the torque demand (curve 902) remains constant, and reaches a minimum with a short delay after the minimum UEGO sensor pump current is reached, due to the nature of using the UEGO sensor output as feedback for the fuel command. Although impairment of the UEGO sensor due to outgassing sealant (without sensor coating) is indicated, no UEGO measurement correction (curve 922) is applied, as the determination of the correction factor takes place under conditions without fuel supply, and fuel continues to be supplied to the engine.

[0097] At time t3, in response to the UEGO sensor pump current exceeding the first pump current threshold for the UEGO sensor to indicate rich fuel conditions (dashed line 914a), the indication of UEGO sensor impairment due to outgassing sealant (without sensor coating) is deactivated. For example, outgassing may be complete (e.g., all gas has been released from the sealant), and the UEGO sensor may function correctly again. In another example, the UEGO sensor transitions from indicating rich fuel conditions because the sensor is coated with sealant. Between time t3 and time t4, as the UEGO sensor pump current (curve 910) increases, fuel consumption (curve 908) increases accordingly. However, the torque demand (curve 902) remains constant, and the exhaust gas temperature (curve 904) remains above the threshold exhaust gas temperature (dashed line 906).

[0098] At time t4, in response to the UEGO sensor pump current (curve 910) exceeding the second pump current threshold for indicating lean fuel conditions (dashed line 914b), an impairment of the UEGO sensor due to outgassing sealant with sensor coating (curve 916) is indicated. Sealant gases released during outgassing have coated the sensor, causing it to measure lean even though fuel consumption (curve 908) is high (e.g., increased from fuel consumption at time t0 for the same torque demand). Between time t4 and time t5, the UEGO measurement correction is not applied, as indicated by curve 922, because fuel continues to be supplied to the engine (curve 908). The high fuel consumption causes the exhaust gas temperature to rise further.

[0099] At time t5, a threshold duration is reached that indicates impairment of the UEGO sensor due to outgassing sealant (with or without sensor coating) without applying the UEGO measurement correction. In response to reaching the threshold duration, the LKV determination is switched to a forward-feed mode. Thus, the incorrect lean value of the UEGO sensor (curve 910) is no longer used as feedback to generate the fuel command, and fuel consumption (curve 908) decreases. With decreasing fuel consumption, the exhaust gas temperature (curve 906) also begins to decrease.

[0100] From time t6, the torque requirement (curve 902) decreases rapidly in response to the driver releasing the pedal. The fuel supply is interrupted, as shown in curve 908, because the engine enters DFSO (Dead Fuel Shutdown). Under these conditions without fuel supply, the UEGO (Unified Fuel Efficiency) measurement correction is learned (e.g., according to the procedure from...). Fig. 8) and then applied as indicated by curve 922. After the UEGO probe measurement was corrected, the UEGO probe correctly measures lean due to the no-fuel conditions. The UEGO probe pump current (curve 910) increases with increasing fuel consumption (curve 908) in response to an increase in driver-requested torque (curve 902). The LKV determination can be switched back to a closed-loop strategy using corrected UEGO probe measurements. The indication of UEGO probe impairment due to outgassing sealant with probe coating remains (curve 916) even after the UEGO measurement correction (curve 922) has been applied and the exhaust gas temperature (curve 904) has dropped below the threshold temperature for causing outgassing (dashed line 906), because the probe coating may be irreversible.

[0101] In this way, impairment of a UEGO sensor due to outgassing sealant can be diagnosed, with or without subsequent sensor recoating. Furthermore, the engine control unit can be adjusted in response to a reported UEGO sensor impairment due to outgassing sealant to prevent incorrect engine operation caused by incorrect fuel delivery. In one example, the LKV (low-speed limiter) can be determined in a forward-feed mode instead of using feedback from the impaired UEGO sensor reading to generate a fuel command. In another example, a measurement correction can be learned to correctly determine the LKV using the impaired UEGO sensor reading, thus generating an appropriate fuel command.

[0102] The technical benefit of detecting damage to the UEGO sensor due to outgassing sealant is that damage to an engine and downstream components, such as a catalytic converter, due to incorrect fuel supply is reduced.

[0103] An exemplary procedure includes: in response to a change in the demand for fuel supply to an engine without a change in the engine power demand at an engine exhaust temperature greater than a threshold temperature, indicating an impairment of a lambda sensor connected to an engine exhaust system by a sealant due to outgassing sealant; and correcting lambda sensor measurements in response to the indication.In the preceding example, indicating impairment of the lambda sensor due to outgassing sealant additionally or, where appropriate, further includes indicating impairment of the lambda sensor due to outgassing sealant without a lambda sensor coating when the lambda sensor measures a rich air-fuel ratio in the engine exhaust in conjunction with reduced fuel consumption; and indicating impairment of the lambda sensor due to outgassing sealant with a lambda sensor coating when the lambda sensor measures a lean air-fuel ratio in the engine exhaust in conjunction with increased fuel consumption. In one or all of the preceding examples, indicating impairment of the lambda sensor due to outgassing sealant with a lambda sensor coating additionally or, where appropriate, further includes indicating a lambda sensor replacement condition.In one or all of the preceding examples, correcting lambda sensor measurements additionally or, where appropriate, further during conditions without fuel supply to the engine, involves operating the lambda sensor at a first lower voltage to produce a first output and a second higher voltage to produce a second output; determining a correction factor for the lambda sensor based on the first and second outputs and a reference sensor output; and multiplying each lambda sensor measurement by the correction factor.In one or all of the preceding examples, the method additionally or optionally further comprises specifying a lambda sensor exchange condition and determining the air-fuel ratio of the engine exhaust in a forward-coupled mode when the correction factor is greater than a threshold; and, in response to the absence of any no-fuel conditions within a threshold time after specifying lambda sensor impairment due to outgassing sealant, determining the air-fuel ratio of the engine exhaust in the forward-coupled mode. In one or all of the preceding examples, additionally or optionally, the first lower voltage is a voltage that does not split water molecules, and the second higher voltage is a voltage that does split water molecules.In one or all of the preceding examples, determining the air-fuel ratio of the engine exhaust gas in forward-coupled mode additionally or optionally involves estimating an air mass charge of cylinders of the engine from an output of an air mass flow sensor and estimating a quantity of fuel supplied to the cylinders from a pulse width of a signal used to actuate fuel injectors of the engine. In one or all of the preceding examples, indicating impairment of the lambda sensor due to outgassing sealant additionally or optionally further involves confirming the absence of impairment of fuel injectors and impairment of an air mass flow sensor.In one or all of the preceding examples, specifying an impairment of the lambda sensor due to outgassing sealant additionally or optionally involves the use of an air-fuel ratio offset that accounts for an impairment of fuel injection devices and an impairment of a mass airflow sensor. In one or all of the preceding examples, the air-fuel ratio offset is additionally or optionally determined based on a difference between a commanded air-fuel ratio and an air-fuel ratio of the engine exhaust measured by the lambda sensor when the engine exhaust temperature is below the threshold temperature.

[0104] Another exemplary procedure includes: indicating impairment of the lambda sensor due to outgassing sealant without a coating on the lambda sensor in response to a lambda sensor coupled to an engine's exhaust system by means of a sealant measuring a rich air-fuel ratio of gas expelled by the engine during a constant engine power demand in conjunction with a reduced fuel demand, and an exhaust gas temperature greater than a threshold temperature; and indicating impairment of the lambda sensor due to outgassing sealant without a coating on the lambda sensor in response to a lambda sensor measuring a lean air-fuel ratio of gas expelled by the engine during a constant engine power demand in conjunction with an increased fuel demand after the exhaust gas temperature has exceeded the threshold temperature.Indicating impairment of the lambda sensor due to outgassing sealant with a lambda sensor coating; and correcting lambda sensor measurements in response to the indication of impairment of the lambda sensor due to outgassing sealant without the lambda sensor coating and in response to the indication of impairment of the lambda sensor due to outgassing sealant with the lambda sensor coating. In the preceding example, correcting lambda sensor measurements additionally or, if appropriate, further during no-fuel conditions includes applying a first lower voltage, which does not split water molecules, and a second higher voltage, which splits water molecules, to the lambda sensor; learning a correction factor for the lambda sensor based on a first and second output produced when the first and second voltages are applied, respectively.and a reference output; and multiplying each lambda sensor measurement by the correction factor. In one or all of the preceding examples, correcting lambda sensor measurements additionally or optionally further includes applying an offset to the air-fuel ratio, determined before the exhaust gas temperature reaches the threshold temperature. In one or all of the preceding examples, the method additionally or optionally further includes, in response to a change in engine power demand, determining lambda sensor impairment due to lag and slow response. In one or all of the preceding examples, determining lambda sensor impairment due to lag and slow response additionally or optionally further includes modulating the air-fuel ratio of the exhaust gas from the engine by a cycle,comprising at least one fat-to-lean transition and at least one lean-to-fat transition; indicating a lambda sensor impairment state in response to at least one of the fat-to-lean response times of the lambda sensor and one of the lean-to-fat response times being greater than a delay threshold, each of the fat-to-lean response time and lean-to-fat response time being a difference between an expected lambda sensor response time and a measured lambda sensor response time; and indicating the lambda sensor impairment state in response to a ratio of the fat-to-lean response time to the lean-to-fat response time being outside a threshold range centered on one.

[0105] An exemplary system comprises: an engine incorporating a plurality of cylinders; fuel injectors designed to supply pressurized fuel to the cylinders; an intake manifold for supplying air to the engine; a mass airflow (MAF) sensor coupled to the intake manifold and designed to measure the amount of air entering the engine; an exhaust manifold for removing exhaust gas from the engine; a lambda sensor coupled to an emissions control device upstream of the exhaust manifold by a sealant and designed to measure the amount of oxygen in the exhaust gas; and a controller storing instructions in non-volatile memory which, when executed, cause the controller to: determine a malfunction state of the fuel injectors; determine a malfunction state of the MAF sensor;and determining a lambda sensor impairment state. In the preceding example, determining the lambda sensor impairment state additionally or optionally includes one or more of the following: determining a delay-type or slow-reacting impairment state and determining an impairment state due to outgassing sealant. In one or all of the preceding examples, determining the impairment state due to outgassing sealant additionally or optionally further includes indicating an impairment of the lambda sensor due to outgassing sealant without coating the lambda sensor with the sealant in response to the lambda sensor measuring a rich exhaust gas air-fuel ratio during a constant engine power demand in conjunction with reduced fuel demand and an exhaust gas temperature greater than a threshold temperature;Indicating an impairment of the lambda sensor due to outgassing sealant with the coating of the lambda sensor with the sealant in response to the lambda sensor measuring a lean air-fuel ratio during constant engine power demand in conjunction with increased fuel demand after the exhaust gas temperature has exceeded the threshold temperature;and indicating the absence of lambda sensor impairment due to outgassing sealant in response to the lambda sensor measuring a stoichiometric air-fuel ratio. In one or all of the preceding examples, the control unit additionally stores, or may store, further instructions in non-volatile memory which, when executed, cause the control unit to: during no-fuel conditions, determine a correction factor for the lambda sensor in response to an indication of lambda sensor impairment due to outgassing sealant without the lambda sensor being coated with the sealant, and in response to an indication of lambda sensor impairment due to outgassing sealant with the lambda sensor being coated with the sealant;and applying the correction factor to each lambda sensor measurement. In one or all of the preceding examples, determining the impairment state due to outgassing sealant additionally or, where appropriate, further includes confirming the absence of impairment of fuel injection devices and impairment of an air mass flow sensor.

[0106] It should be noted that the exemplary control and estimation sequences contained herein can be used with various engine and / or vehicle system designs. The control methods and sequences disclosed herein can be stored as executable instructions in non-volatile memory and executed by the control system, including the controller, in combination with the various sensors, actuators, and other engine components. The specific sequences described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Accordingly, various illustrated operations, steps, and / or functions can be performed in the illustrated sequence or in parallel, or in some cases, omitted.Similarly, the processing sequence is not strictly necessary to achieve the features and advantages of the exemplary embodiments described here, but is provided for easier illustration and description. One or more of the illustrated processes, steps, and / or functions can be repeated depending on the specific strategy employed. Furthermore, the described processes, steps, and / or functions can graphically represent code that is to be programmed in non-volatile memory of the computer-readable storage medium in the engine control system, whereby the described processes are executed by carrying out the instructions in a system that includes the various engine hardware components in combination with the electronic control unit.

[0107] It is understood that the interpretations and processes disclosed herein are exemplary in nature and that these specific embodiments are not to be interpreted in a restrictive sense, as numerous variations are possible. For example, the foregoing technology can be applied to V-6, I-4, I-6, V-12, 4-cylinder boxer, and other engine types. The subject matter of this disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and designs, and further features, functions, and / or properties disclosed herein.

Claims

[1] Procedure, encompassing: in response to a change in the demand for fuel supply to an engine without a change in the engine power demand at an engine exhaust temperature greater than a threshold temperature, indicating impairment of a lambda sensor connected to an engine exhaust system by a sealant, due to outgassing sealant; and Correcting lambda sensor measurements in response to the input. [2] Method according to claim 1, wherein indicating an impairment of the lambda probe due to outgassing sealant further comprises: Indicating impairment of the lambda sensor due to outgassing sealant without a coating on the lambda sensor, when the lambda sensor measures a rich air-fuel ratio in the engine exhaust in conjunction with reduced fuel consumption; and Indicating impairment of the lambda sensor due to outgassing sealant with a coating of the lambda sensor, when the lambda sensor measures a lean air-fuel ratio of the engine exhaust in conjunction with an increased fuel demand. [3] Method according to claim 2, wherein specifying an impairment of the lambda probe due to outgassing sealant with the coating of the lambda probe further includes specifying a replacement condition for the lambda probe. [4] Method according to claim 1, wherein correcting measurements of the lambda probe further comprises: During conditions without fuel supply to the engine, the lambda sensor operates at a first lower voltage to produce a first output, and a second higher voltage to produce a second output; Determining a correction factor for the lambda sensor based on the first and second outputs and a reference sensor output; and Multiply each lambda sensor measurement by the correction factor. [5] The method of claim 4, further comprising: Specifying a replacement condition for the lambda sensor and determining the air-fuel ratio of the engine exhaust in a forward-coupled mode when the correction factor is greater than a threshold value; and In response to the absence of fuel-free conditions within a threshold duration following the indication of lambda sensor impairment due to outgassing sealant, the air-fuel ratio of the engine exhaust is determined in forward-coupled mode. [6] Method according to claim 4, wherein the first lower voltage is a voltage that does not split water molecules, and the second higher voltage is a voltage that splits water molecules. [7] Method according to claim 5, wherein determining the air-fuel ratio of the engine exhaust in forward-coupled mode includes estimating an air mass charge of cylinders of the engine based on an output of an air mass flow sensor and estimating an amount of fuel supplied to the cylinders based on a pulse width of a signal used to actuate fuel injection devices of the engine. [8] Method according to claim 1, wherein indicating an impairment of the lambda probe due to outgassing sealant further includes confirming the absence of an impairment of fuel injection devices and an impairment of an air mass flow sensor. [9] Method according to claim 1, wherein indicating an impairment of the lambda probe due to outgassing sealant further includes using an offset of the air-fuel ratio that takes into account an impairment of fuel injection devices and an impairment of an air mass flow sensor. [10] Method according to claim 9, wherein the offset of the air-fuel ratio is determined on the basis of a difference between a commanded air-fuel ratio and an air-fuel ratio of the engine exhaust gas measured by the lambda probe when the engine exhaust gas temperature is less than the threshold temperature. [11] System, encompassing: an engine that includes a large number of cylinders; Fuel injection devices designed to supply pressurized fuel to the cylinders; an intake duct to supply air to the engine; an air mass flow (MAF) sensor that is coupled to the intake duct and is designed to measure the amount of air entering the engine; an exhaust duct for removing exhaust gas from the engine; a lambda sensor, which is coupled to an emission control device upstream of the exhaust gas channel by means of a sealing agent and is designed to measure the amount of oxygen in the exhaust gas; and a controller that stores instructions in non-volatile memory which, when executed, cause the controller to do the following: Determining the impairment status of the fuel injection devices; Determining the impairment status of the MAF sensor; and Determining the impairment status of the lambda sensor, where determining the impairment state of the lambda probe includes determining an impairment state of delay type or slow-reacting type and determining an impairment state due to outgassing sealant. [12] System according to claim 11, wherein determining the state of impairment due to outgassing sealant further comprises: Indicating an impairment of the lambda sensor due to outgassing sealant without a coating of the lambda sensor with the sealant in response to the lambda sensor measuring a rich air-fuel ratio of the exhaust gas during a constant engine power demand in conjunction with a reduced fuel demand and an exhaust gas temperature greater than a threshold temperature; Indicating an impairment of the lambda sensor due to outgassing sealant with the coating of the lambda sensor with the sealant in response to the lambda sensor measuring a lean air-fuel ratio during constant engine power demand in conjunction with increased fuel demand after the exhaust gas temperature has exceeded the threshold temperature; and Indicating the absence of impairment of the lambda sensor due to outgassing sealant in response to the lambda sensor measuring a stoichiometric air-fuel ratio. [13] System according to claim 12, wherein the controller stores further instructions in non-volatile memory which, when executed, cause the controller to: Determining a correction factor for the lambda sensor during conditions without fuel supply in response to a report of lambda sensor impairment due to outgassing sealant without coating the lambda sensor with the sealant, and in response to a report of lambda sensor impairment due to outgassing sealant with coating the lambda sensor with the sealant; and Apply the correction factor to each measurement of the lambda sensor. [14] System according to claim 12, wherein determining the impairment state due to outgassing sealant further includes confirming the absence of impairment of the fuel injection devices and impairment of the air mass flow sensor.

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