METHOD AND SYSTEMS FOR DIAGNOSTICING A FOUR-LAMBDA PROBE SYSTEM

Abstract

Systems and methods for evaluating the operation of a plurality of upstream and downstream lambda sensors are disclosed. In one example, the air-fuel patterns can be arranged in a sequence to reduce the time required to evaluate upstream and downstream lambda sensors. The lambda sensor evaluation can be suitable for detecting sensor miswiring and sensor wear.

Description

Area

[0001] The present description relates to a system and method for verifying the intended operation of four wideband lambda sensors in an engine system. General state of the art

[0002] An internal combustion engine can be configured with lambda sensors. The lambda sensors can provide feedback for adjusting the engine's air-fuel ratio. Furthermore, the lambda sensors can include wideband lambda sensors (universal exhaust gas oxygen sensors - UEGOs) and / or heated lambda sensors (heated exhaust gas oxygen sensors - HEGOs). The UEGOs can be positioned to detect exhaust gases that originate directly from the engine cylinders, and the HEGOs can be positioned to detect gases that are located within or downstream of a catalytic converter. Brief description

[0003] A method for operating an engine is provided. The method comprises issuing a command to each of two sets of fuel injectors to generate a stoichiometric, rich, or lean air-fuel ratio in each of two pairs of cylinders and to generate at least four different air-fuel ratio patterns of the cylinders in the two pairs of cylinders during at least four different time intervals of lambda sensor diagnostics. In this way, it is possible to identify, initially or during and throughout the entire lifespan of a vehicle, whether a lambda sensor may be miswired, outputting an unexpected signal, or not responding in an expected manner.

[0004] It is understood that the foregoing summary is provided to introduce, in simplified form, a selection of concepts that are further described in the detailed description. It is not intended to identify key features of the claimed subject matter, the scope of which is defined solely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address any of the disadvantages mentioned above or in any part of this disclosure. Brief description of the drawings

[0005] The advantages described herein will become more fully apparent from reading an example of an embodiment, referred to in this document as the detailed description, either alone or with reference to the drawings, in which the following applies: Fig. Figure 1 is a schematic representation of a single cylinder of an engine; Fig. Figure 2 is a schematic representation of an exemplary eight-cylinder engine with lambda sensors; Fig. Figures 3-7 show exemplary air-fuel control sequences for diagnosing an engine system that includes four UEGO sensors and two HEGO sensors; and Fig. Figure 8 shows a flowchart of an exemplary procedure for operating an engine and diagnosing lambda sensors. Detailed description

[0006] This description concerns the diagnosis of the operation of a multitude of lambda sensors in the exhaust system of an internal combustion engine. The diagnosis can evaluate both UEGO and HEGO sensors. Furthermore, the system can include four UEGO sensors and two HEGO sensors. The diagnosis can be configured to minimize the time required to determine whether the UEGO and HEGO sensors are operating as desired. The time required to evaluate the lambda sensors can be reduced by developing air-fuel control patterns that provide insight into more than one aspect of lambda sensor operation. Additionally, the sequence in which the air-fuel control patterns are applied can also contribute to reducing the duration of lambda sensor diagnostics. The engine can be an internal combustion engine, as described in Fig. 1 and Fig. 2 shown. Different patterns of air-fuel mixtures can be supplied to the internal combustion engine, as shown in Fig. Figures 3-7 are shown to aid in lambda sensor diagnostics. A procedure for operating an engine using one of the described air-fuel ratio sequences is shown in Figure 3-7. Fig. 8 shown.

[0007] A bank of four cylinders can be controlled based on the output of a single UEGO sensor. However, it may be possible to determine the air-fuel ratios of each cylinder in a bank more accurately if a single UEGO sensor is configured to sample exhaust gases from two of the four cylinders. Thus, if one UEGO sensor is used to sample exhaust gases from two cylinders in one cylinder bank, and a second UEGO sensor is used to sample exhaust gases from two other cylinders in the same cylinder bank, the accuracy of air-fuel ratio estimates for cylinders in that cylinder bank can be improved.

[0008] More accurate air-fuel ratio readings can enable more precise control of an engine's air-fuel ratios, thereby reducing engine emissions. However, additional oxygen sensors can lead to more complex diagnostics and longer diagnostic evaluation times. This longer and more complex diagnostic process can slow down vehicle assembly lines and reduce productivity. Therefore, it may be desirable to provide a method for diagnosing four upstream and two downstream oxygen sensors without significantly increasing system complexity or the execution time for oxygen sensor diagnostics.

[0009] The inventors recognized that lambda sensor diagnostics could be developed to reduce the time required to perform diagnostics and thoroughly check a large number of lambda sensors, even when the number of lambda sensors is relatively large. To implement this insight, the inventors developed a method for operating an engine that includes: issuing a command to each of two groups of fuel injectors to generate a stoichiometric, rich, or lean air-fuel ratio in each of two pairs of cylinders, and generating at least four different air-fuel ratio patterns of the cylinders in the two pairs of cylinders during at least four different time intervals of a lambda sensor diagnostic.

[0010] By issuing air-fuel ratio commands to different cylinders and generating air-fuel ratio patterns, it is possible to reduce the time required to execute a lambda sensor diagnostic sequence. Furthermore, the air-fuel ratio pattern can be generated in such a way that each lambda sensor is actuated in a manner that can reveal the presence or absence of wear or unexpected lambda sensor operation. Consequently, an entire set of lambda sensors in a vehicle can be thoroughly evaluated in a short period of time.

[0011] The present description can offer several advantages. In particular, the approach can provide faster diagnostics. Furthermore, the approach can reduce the diagnostic complexity of a lambda sensor by generating a few highly useful air-fuel ratio patterns. Additionally, the approach can enable efficient catalyst operation while a lambda sensor diagnosis is performed.

[0012] The aforementioned advantages, as well as other advantages and features of the present description, will become readily apparent from the following detailed description, whether considered on its own or in conjunction with the accompanying drawings.

[0013] With reference to Fig. 1 is an internal combustion engine 10 comprising a plurality of cylinders, one of which is in Fig. As shown in Figure 1, the engine 10 is controlled by an electronic engine control unit 12. The engine 10 includes a combustion chamber 30 and cylinder walls 32 with a piston 36 positioned therein and connected to a crankshaft 40. A flywheel 97 and a ring gear 99 are coupled to the crankshaft 40. A starter 96 includes a pinion shaft 98 and a pinion 95. The pinion shaft 98 can selectively advance the pinion 95 to engage the ring gear 99. The starter 96 can be mounted directly on the front or rear of the engine. In some examples, the starter 96 can selectively supply torque to the crankshaft 40 via a power transmission device (e.g., a chain). In one example, the starter 96 is in a resting state when it is not engaged with the engine crankshaft.According to the illustration, the combustion chamber 30 is connected to an intake manifold 44 and an exhaust manifold 48 via an intake valve 52 and an exhaust valve 54, respectively. Each intake and exhaust valve can be operated by an intake cam 51 and an exhaust cam 53. The position of the intake cam 51 can be determined by an intake cam sensor 55. The position of the exhaust cam 53 can be determined by an exhaust cam sensor 57.

[0014] As shown, the direct fuel injection device 66 is positioned to inject fuel directly into cylinder 35, a process known to those skilled in the art as direct injection. The direct fuel injection device 66 delivers liquid fuel proportionally to a voltage pulse width or fuel injection pulse width of a signal from the control unit 12. The fuel is supplied to the fuel injection device 66 by a fuel system (not shown) comprising a fuel tank, a fuel pump, and a fuel distributor (not shown). Alternatively or additionally, the engine 10 can also include a port fuel injection device 69 for each cylinder, a process known to those skilled in the art as port fuel injection.The intake manifold fuel injection device 69 delivers liquid fuel proportionally to a voltage pulse width or fuel injection device pulse width of a signal from the controller 12. Fuel can be supplied to the intake manifold fuel injection device 69 via the fuel system (not shown).

[0015] According to the illustration, the intake manifold 44 communicates with an optional electronic throttle 62, which sets the position of a throttle valve 64 to control the airflow from an air inlet 42 to the intake manifold 44. In some examples, the throttle 62 and the throttle valve 64 can be positioned between the intake valve 52 and the intake manifold 44 such that the throttle 62 is a single throttle.

[0016] A distributorless ignition system 88 provides a spark to the combustion chamber 30 via a spark plug 92 in response to the control unit 12. According to the diagram, a wideband lambda sensor (universal exhaust gas oxygen sensor - UEGO sensor) 126 is coupled to the exhaust manifold 48 upstream of a catalytic converter 70. Alternatively, the UEGO sensor 126 can be replaced by a binary lambda sensor.

[0017] In one example, catalyst 70 can contain multiple catalyst honeycomb structures. In another example, multiple emission control devices, each with multiple honeycomb structures, can be used. In another example, catalyst 70 can be a three-way catalyst.

[0018] Control 12 is in Fig. 1 is represented as a conventional microcomputer, which includes: a microprocessor unit 102, input / output ports 104, a read-only memory 106 (e.g. persistent memory), a random access memory 108, a keep-alive memory 110 and a conventional data bus.According to the illustration, in addition to the signals discussed previously, the control unit 12 receives various signals from sensors coupled to the engine 10, including: an engine coolant temperature (ECT) from a temperature sensor 112 coupled to a cooling sleeve 114; a position sensor 134 coupled to a driver-activated pedal 130 to detect the distance it has been moved by a person 132; a position sensor 154 coupled to a brake caliper control pedal 150 to detect the distance it has been moved by a person 132; a manifold pressure (MAP) measurement from a pressure sensor 122 coupled to the intake manifold 44; an engine position sensor from a Hall sensor 118 detecting the position of the crankshaft 40; and a measurement of the mass of air entering the engine from a sensor 120. and a measurement of a throttle position from a sensor 58.Air pressure can also be detected for processing by the controller 12 (sensor not shown). In a preferred aspect of the present description, the motor position sensor 118 generates a predetermined number of evenly spaced pulses at each revolution of the crankshaft, from which the engine speed (RPM) can be determined.

[0019] In some examples, the motor can be coupled to an electric motor / battery system in a hybrid vehicle. Furthermore, the controller can receive 12 inputs and communicate states, such as component wear, to illuminate a light, or alternatively communicate these to a human-machine interface 171 (touchscreen display and input device).

[0020] During operation, each cylinder within the engine 10 typically goes through a four-stroke cycle: the cycle includes the intake stroke, the compression stroke, the power stroke, and the exhaust stroke. During the intake stroke, the exhaust valve 54 generally closes and the intake valve 52 opens. Air is drawn into the combustion chamber 30 via the intake manifold 44, and the piston 36 moves toward the bottom of the cylinder to increase the volume within the combustion chamber 30. The position at which the piston 36 is near the bottom of the cylinder and at the end of its stroke (e.g., when the combustion chamber 30 has reached its maximum volume) is typically referred to by those skilled in the art as bottom dead center (BDC). During the compression stroke, the intake valve 52 and the exhaust valve 54 are closed. The piston 36 moves toward the cylinder head to compress the air within the combustion chamber 30.The point at which the piston 36 is closest to the cylinder head at the end of its stroke (e.g., when the combustion chamber 30 has its smallest volume) is usually referred to by those skilled in the art as top dead center (TDC). In a process referred to below as injection, fuel is introduced into the combustion chamber. In a process referred to below as ignition, the injected fuel is ignited by known ignition means, such as the spark plug 92, resulting in combustion.

[0021] During the power stroke, the expanding gases push the piston 36 back to bottom dead center (BDC). The crankshaft 40 converts the piston movement into a torque of the crankshaft. Finally, during the exhaust stroke, the exhaust valve 54 opens to release the burnt air-fuel mixture to the exhaust manifold 48, and the piston returns to top dead center (TDC). It should be noted that the above is shown only as an example, and that the timing of the opening and / or closing of the intake and exhaust valves can vary, for example, to provide positive or negative valve overlap, late closing of the intake valve, or various other examples.

[0022] Now, the focus will shift to... Fig. Reference is made to Figure 2, which shows a top view 200 of motor 10. Motor 10 is the same motor as in Fig. 1 shown, however, are in Fig. Figure 2 shows all engine cylinders. In this example, the engine cylinders are numbered 1 through 8. Air is supplied to the cylinders via the intake manifold 44. A first bank of cylinders, B1, includes cylinders 1-4, and a second bank of cylinders, B2, includes cylinders 5-8. Cylinders 1-4 are shown in fluid connection with the exhaust manifold 48, and cylinders 5-8 are shown in fluid connection with the exhaust manifold 220. Each of the cylinders 1-8 includes fuel injectors, a spark plug, and intake / exhaust valves, as shown in Figure 2. Fig. 1 shown. A front 290 and a rear 292 of the motor 10 are as shown.

[0023] A first lambda sensor 126 (UEGO) is configured, according to the diagram, to detect exhaust gases from cylinders numbered 1 and 2 at an exhaust gas junction point 250 for cylinders 1 and 2. A second lambda sensor 204 (UEGO) is configured, according to the diagram, to detect exhaust gases from cylinders 3 and 4 at an exhaust gas junction point 252 for cylinders 3 and 4. A third lambda sensor 206 (UEGO) is configured, according to the diagram, to detect exhaust gases from cylinders numbered 5 and 7 at an exhaust gas junction point 254 for cylinders 5 and 7. A fourth lambda sensor 208 (UEGO) is configured, according to the diagram, to detect exhaust gases from cylinders 6 and 8 at an exhaust gas junction point 256 for cylinders 6 and 8. There are no cylinders located downstream of any of the exhaust gas sensors, as indicated by arrows 230 and 240, in accordance with the exhaust gas flow from the cylinders.

[0024] The output of the first lambda sensor 126 can be used as air-fuel ratio feedback to control the fuel supplied to cylinders 1 and 2 via port and / or direct fuel injection systems. The output of the second lambda sensor 204 can be used as air-fuel ratio feedback to control the fuel supplied to cylinders 3 and 4 via port and / or direct fuel injection systems. The output of the third lambda sensor 206 can be used as air-fuel ratio feedback to control the fuel supplied to cylinders 5 and 7 via port and / or direct fuel injection systems.The output of the fourth lambda sensor 208 can be used as air-fuel ratio feedback to control the fuel supplied to cylinders 6 and 8 via port fuel injection and / or direct fuel injection systems. Thus, the first lambda sensor 126 is assigned to cylinders 1 and 2, the second lambda sensor 204 to cylinders 3 and 4, the third lambda sensor 206 to cylinders 5 and 7, and the fourth lambda sensor 208 to cylinders 6 and 8.

[0025] The engine 10 also includes a first downstream lambda sensor 224, configured to detect exhaust gases from cylinder bank B1 at a point inside or downstream of the catalyst 70, and a second downstream lambda sensor 226, configured to detect exhaust gases from cylinder bank B2 at a point inside or downstream of the catalyst 270. The downstream lambda sensor 224 or 226 can be a heated lambda sensor (HEGO), which can be considered a dual-state sensor.

[0026] The system made of Fig. 1 and Fig. 2 provides an engine system comprising: an internal combustion engine comprising a first bank of cylinders and a second bank of cylinders, and at least eight fuel injection devices, comprising at least one fuel injection device for each cylinder of the first bank of cylinders and at least one for each cylinder of the second bank; a first oxygen sensor configured to detect gases discharged from a first and a second cylinder of the first bank of cylinders; a second oxygen sensor configured to detect gases discharged from a third and a fourth cylinder of the first bank of cylinders; a third oxygen sensor configured to detect gases discharged from a fifth and a sixth cylinder of the second bank of cylinders; a fourth oxygen sensor configured to detect gases,which are extracted from a seventh and an eighth cylinder of the second bank of cylinders; and a controller comprising executable instructions stored in non-transient memory that cause the controller to command the at least eight fuel injectors to perform one of a stoichiometric, rich, or lean air-fuel ratio in each cylinder of the first bank of cylinders and each cylinder of the second bank, and to generate at least four distinct air-fuel ratio patterns of the cylinders in the first bank of cylinders and the second bank of cylinders during at least four distinct time intervals of a lambda sensor diagnostic sequence. In a first example, the engine system includes the at least four distinct air-fuel ratio patterns of the cylinders being arranged in a sequence,to reduce the duration of the lambda sensor diagnostic sequence. In a second example, which may include the first example, the engine system further includes additional executable instructions that cause the controller to compare outputs from the first, second, third, and fourth lambda sensors with the at least four distinct air-fuel ratio patterns of the cylinders and to identify the presence or absence of miswiring from each of the first, second, third, and fourth lambda sensors. In a third example, which may include one or both of the first and second examples, the engine system further includes additional executable instructions that cause the controller to compare outputs from the first, second, third, and fourth lambda sensors.to compare the outputs of the third and fourth oxygen sensors with the at least four different air-fuel ratio patterns of the cylinders and to identify the presence or absence of wear on each of the first, second, third, and fourth oxygen sensors. In a fourth example, which may include one or more of the first through third examples, the engine system further comprises a first downstream oxygen sensor located in a fifth exhaust port and comparing outputs of the first downstream oxygen sensor with the at least four different air-fuel ratio patterns of the cylinders and additional executable instructions to identify the presence or absence of miswiring of the first downstream oxygen sensor. In a fifth example,In a sixth example, which may include one or more of the first through fourth examples, the engine system further comprises a second downstream oxygen sensor located in a sixth exhaust port, and additional executable instructions for comparing outputs from the second downstream oxygen sensor with the at least four distinct air-fuel ratio patterns of the cylinders and identifying the presence or absence of any miswiring of the second downstream oxygen sensor. In a sixth example, which may include one or more of the first through fifth examples, the engine system further comprises additional executable instructions that cause the control unit to indicate the presence or absence of any wear from each of the first downstream oxygen sensors and the second downstream oxygen sensor.

[0027] Now, with reference to Fig. 3 Table 350 is shown, illustrating an air-fuel ratio sequence for diagnosing four different upstream oxygen sensors (UEGOs). Furthermore, the air-fuel ratio sequence shown in Fig. Figure 3 shows how this can be used to diagnose two different downstream oxygen sensors (HEGOs). Table 350 includes a first cell 302 that excludes rows 305 and 306 to indicate that these rows and their associated columns are assigned to the first bank of cylinders, B1. Table 350 also includes a second cell 304 that excludes rows 307 and 308 to indicate that these rows and their associated columns are assigned to the second bank of cylinders, B2. Table 350 includes a first column 310 that accommodates indicators for cylinder pairs (e.g.,P1 indicates the first cylinder pair (cylinders one and two), P2 the second cylinder pair (cylinders three and four), P3 the third cylinder pair (cylinders five and seven), and P4 the fourth cylinder pair (cylinders six and eight), which are assigned air-fuel ratios applied during phases of the lambda sensor diagnostic sequence shown in Table 350. The five phases of the lambda sensor diagnostic sequence are shown in columns 312–320.

[0028] Air-fuel ratios burned in cylinders (commanded air-fuel ratios) and emitted during the air-fuel sequence for diagnosing lambda sensors are indicated by the letters S (stoichiometric air-fuel ratio), R (rich air-fuel ratio), and L (lean air-fuel ratio). For example, line 305, column 312 indicates that the phase one air-fuel ratio for cylinder pair P1 is a stoichiometric air-fuel ratio. Furthermore, line 306, column 314 indicates that the phase two air-fuel ratio for cylinder pair P2 is a stoichiometric air-fuel ratio, and so on. Along the bottom of Table 350, time intervals (e.g. t0-t4) are shown to illustrate which time intervals are assigned to the air-fuel ratios during the air-fuel ratio sequence for diagnosing lambda sensors.For example, the time interval t0 indicates that column 312 contains air-fuel mixture designations associated with the first phase of the air-fuel ratio sequence for diagnosing lambda sensors. The time interval t1 indicates that column 314 contains air-fuel mixture designations associated with the second phase of the air-fuel ratio sequence for diagnosing lambda sensors, and so on. The time intervals t0-t4 can have different durations, with time interval t1 immediately following time interval t0, time interval t2 immediately following time interval t1, and so on.

[0029] The first phase of the air-fuel sequence for diagnosing four upstream and two downstream lambda sensors in the time interval t0 involves burning stoichiometric air-fuel mixtures in cylinder pairs P1, P2, P3, and P4. The second phase of the air-fuel sequence for diagnosing four upstream and two downstream lambda sensors in the time interval t1 involves burning a rich air-fuel mixture in cylinder pair P1, a stoichiometric air-fuel mixture in cylinder pair P2, a lean air-fuel mixture in cylinder pair P3, and a stoichiometric air-fuel mixture in cylinder pair P4.The third phase of the air-fuel sequence for diagnosing four upstream lambda sensors and two downstream lambda sensors in the time interval t2 involves burning a stoichiometric air-fuel mixture in cylinder pair P1, burning a rich air-fuel mixture in cylinder pair P2, burning a stoichiometric air-fuel mixture in cylinder pair P3, and burning a lean air-fuel mixture in cylinder pair P4. The fourth phase of the air-fuel sequence for diagnosing four upstream lambda sensors and two downstream lambda sensors in the time interval t3 involves burning a rich air-fuel mixture in cylinder pair P1, burning a rich air-fuel mixture in cylinder pair P2, burning a lean air-fuel mixture in cylinder pair P3, and burning a lean air-fuel mixture in cylinder pair P4.The fifth phase of the air-fuel sequence for diagnosing four upstream lambda sensors and two downstream lambda sensors in time interval t4 involves burning a lean air-fuel mixture in cylinder pair P1, burning a lean air-fuel mixture in cylinder pair P2, burning a rich air-fuel mixture in cylinder pair P3, and burning a rich air-fuel mixture in cylinder pair P4.

[0030] The air-fuel sequence for diagnosing lambda sensors, as in Fig. As shown in Figure 3, this method can be used to determine the presence or absence of miswired lambda sensors, for example, by evaluating the wiring of each upstream lambda sensor in relation to each control input of an upstream lambda sensor. Lambda sensor diagnostics can involve sets of air-fuel ratio commands (implemented by fuel commands) such that each cylinder pair receives a different command than the other cylinder pairs in at least one command.

[0031] Parentheses {} are used here to specify air-fuel ratio commands for a phase of the air-fuel sequence for diagnosing lambda sensors. Within the parentheses, four air-fuel ratio commands (e.g., {S,R,R,S}), one for each cylinder pair, are shown.The leftmost air-fuel ratio command in the parentheses represents the fuel command for the first pair of cylinders (cylinders number one and two), the second air-fuel ratio command from the left in the parentheses represents the air-fuel ratio command for the second pair of cylinders (cylinders number three and four), the third air-fuel ratio command from the left in the parentheses represents the air-fuel ratio command for the third pair of cylinders (cylinders number five and seven), and the fourth air-fuel ratio command from the leftmost parentheses represents the air-fuel ratio command for the fourth pair of cylinders (cylinders number six and eight). Herein, U. k represents an upstream lambda sensor, which is connected to a k-th cylinder pair P k is assigned, where k is an integer from 1 to 4. nrepresents a control input for an upstream lambda sensor output, which is assigned to the cylinder pair P n is assigned, where n is an integer from 1 to 4. The notation U k →I n specifies a lambda sensor k connected to a control input n. Therefore, if k=n, U k correctly wired. If k≠n, then U k miswired.

[0032] A {S,S,S,R} command sequence can be used to detect miswiring of upstream oxygen sensor number four with oxygen sensor inputs one (U4→I1), two (U4→I2), and three (U4→I3), since cylinder pair P4 is the only cylinder pair to which the rich command is given. It should be noted that the command sequence {S,S,S,L} can be used to detect miswiring of upstream oxygen sensor number four in a similar manner.

[0033] A {S,S,R,R} command sequence can be applied to detect a subset of miswirings from upstream oxygen sensor number four with oxygen sensor inputs one (U4→I1) and two (U4→I2), since both cylinder pairs P3 and P4 are given the rich command. It should be noted that a {S,S,L,L} command can be applied to detect a miswiring of upstream oxygen sensor number four in a similar manner. Furthermore, {S,S,R,R} can be applied to detect a subset of miswirings of upstream oxygen sensor number three.

[0034] A {S,R,S,R} command sequence can be used to detect a subset of miswiring from upstream oxygen sensor number four with oxygen sensor inputs one (U4→I1) and three (U4→I3), since both cylinder pairs P2 and P4 are given the rich command. It should be noted that combining the commands {S,S,R,R} and {S,R,S,R} allows the detection of miswiring from upstream oxygen sensor number four with upstream inputs one, two, and three. Furthermore, combining the sequences {S,S,L,L} and {S,L,S,L}; {S,S,R,R} and {S,L,S,L}; and {S,S,L,L} and {S,R,S,R} enable the detection of a miswiring of the fourth upstream lambda sensor with the first, second and third upstream lambda sensor inputs.

[0035] An {S,S,L,R} command sequence can be applied to detect miswiring from upstream oxygen sensor number four with oxygen sensor inputs one (U4→I1), two (U4→I2), and three (U4→I3), since cylinder pair P4 is the only cylinder pair to which the rich command is given. Furthermore, the {S,S,L,R} command sequence can be applied to detect miswiring from upstream oxygen sensor number three with oxygen sensor inputs one (U3→I1), two (U3→I2), and four (U3→I4). A command {S,S,L,R} may be preferred over a command {S,S,S,R} because it can be used to identify any possible miswiring of the two upstream lambda sensors assigned to the third and fourth cylinder pairs, whereas {S,S,S,R} can only identify any possible miswiring with the upstream lambda sensor assigned to the fourth cylinder pair.

[0036] An {R,R,R,S} or a {L,L,L,S} command sequence can be applied to detect miswiring from the upstream lambda sensor number four with lambda sensor inputs one (U4→I1), two (U4→I2) and three (U4→I3), since the cylinder pair P4 is the only cylinder pair to which the command for a stoichiometric air-fuel ratio is given.

[0037] During a lambda sensor diagnostic, an air-fuel ratio command is issued for pairs of engine cylinders, as shown in Table 350. Specifically, a command for {S,S,S,S} is issued during time interval t0, a command for {R,S,L,S} is issued during time interval t1, a command for {S,R,S,L} is issued during time t2, a command for {R,R,L,L} is issued during time interval t3, and a command for {L,L,R,R} is issued during time interval t4. This air-fuel ratio command sequence allows each upstream lambda sensor (in at least one phase) to be exposed to exhaust gases from a specific pair of cylinders that have burned a rich air-fuel mixture. These sequences of commanded air-fuel ratios enable lambda sensor diagnostics to verify whether each upstream lambda sensor is responding to combustion products of a rich air-fuel mixture or not.The command {R,R,L,L} at time t3 causes the upstream oxygen sensor assigned to P1 to be exposed to combustion products of rich air-fuel mixtures in the first cylinder pair (P1), so that it can be determined whether the upstream oxygen sensor assigned to the first cylinder pair (P1) responds with a rich air-fuel mixture reading or not. Similarly, the command {R,R,L,L} during time interval t3 causes the upstream oxygen sensor assigned to P2 to be exposed to combustion products of rich air-fuel mixtures in the second cylinder pair (P2), so that it can be determined whether the upstream oxygen sensor assigned to the second cylinder pair (P2) responds with a rich air-fuel mixture reading or not.The command {L,L,R,R} during time interval t4 causes the upstream oxygen sensor assigned to P3 to be exposed to combustion products of rich air-fuel mixtures in a third cylinder pair (P3), so that it can be determined whether the upstream oxygen sensor assigned to the third cylinder pair (P3) responds with a rich air-fuel mixture reading or not. Similarly, the command {L,L,R,R} during time interval t4 causes the upstream oxygen sensor assigned to P4 to be exposed to combustion products of rich air-fuel mixtures in a fourth cylinder pair (P4), so that it can be determined whether the upstream oxygen sensor assigned to the fourth cylinder pair (P4) responds with a rich air-fuel mixture reading or not.

[0038] The sequence of commanded air-fuel ratios that is in Fig. As shown in Figure 3, the lambda sensor diagnostics also allow verification of whether each upstream lambda sensor reacts to combustion products of a lean air-fuel mixture. The command {R,R,L,L} during the time interval t4 causes the upstream lambda sensor assigned to P1 to be exposed to combustion products of rich air-fuel mixtures in a first cylinder pair (P1), so that it can be determined whether the upstream lambda sensor assigned to the first cylinder pair (P1) reacts with an indication of a rich air-fuel mixture or not.Furthermore, the command {R,R,L,L} during time interval t4 causes the upstream oxygen sensor assigned to P2 to be exposed to combustion products of rich air-fuel mixtures in a second cylinder pair (P2), so that it can be determined whether the upstream oxygen sensor assigned to the second cylinder pair (P2) responds with a reading of a rich air-fuel mixture or not. The command {R,R,L,L} during time interval t3 causes the upstream oxygen sensor assigned to P3 to be exposed to combustion products of lean air-fuel mixtures in a third cylinder pair (P3), so that it can be determined whether the upstream oxygen sensor assigned to the third cylinder pair (P3) responds with a reading of a lean air-fuel mixture or not.Additionally, during the time interval t3, the command {R,R,L,L} causes the upstream lambda sensor assigned to P4 to be exposed to combustion products of lean air-fuel mixtures in a fourth cylinder pair (P4), so that it can be determined whether the upstream lambda sensor assigned to the fourth cylinder pair (P4) responds with an indication of a lean air-fuel mixture or not.

[0039] As mentioned previously, the air-fuel sequence can be used to diagnose lambda sensors, as in Fig. Figure 3 shows how to use this command to determine the presence or absence of miswired upstream oxygen sensors. Specifically, the command {R,S,L,S} during time interval t1 creates a rich air-fuel mixture in the first cylinder pair (P1), allowing for the evaluation of any miswiring of the upstream oxygen sensor assigned to the first cylinder pair (P1). The command {S,R,S,L} during time interval t2 creates a rich air-fuel mixture in the second cylinder pair (P2), allowing for the evaluation of any miswiring of the upstream oxygen sensor assigned to the second cylinder pair (P2). The command {R,S,L,S} during the time interval t1 creates a lean air-fuel mixture in the third cylinder pair (P3), so that a miswiring of the upstream lambda sensor assigned to the third cylinder pair (P3) can be evaluated.The command {S,R,S,L} during the time interval t2 creates a lean air-fuel mixture in the fourth cylinder pair (P4), so that a wiring error of the upstream lambda sensor assigned to the fourth cylinder pair (P4) can be evaluated. Thus, the only command for the rich / lean air-fuel ratio at the k-th cylinder pair (P4) can be used. k ) to a single rich / lean reading at the nth control input, where k=n indicates that the lambda sensor, which P k is assigned, is correctly wired to the k-th control input, where k≠n indicates that the lambda sensor, which P k is assigned to, but is incorrectly wired to the nth control input.

[0040] The sequence of commanded air-fuel ratios that is in Fig. As shown in Figure 3, the lambda sensor diagnostics also allow verification of whether each downstream lambda sensor responds to combustion products of a rich air-fuel mixture. Specifically, the command {R,R,L,L} generates a rich air-fuel mixture in the first cylinder bank (B1) during time interval t3, enabling the control unit to determine whether the first downstream lambda sensor of the first bank responds with a rich reading to the exhaust gases of rich air-fuel mixtures in the first cylinder bank. Additionally, the command {L,L,R,R} generates a rich air-fuel mixture in the second cylinder bank (B2) during time interval t4, allowing the control unit to determine whether the downstream lambda sensor of the second bank responds with a rich reading to the exhaust gases of rich air-fuel mixtures in the second cylinder bank.

[0041] The sequence of commanded air-fuel ratios that is in Fig. As shown in Figure 3, the lambda sensor diagnostics also allow verification of whether each downstream lambda sensor responds to combustion products of a lean air-fuel mixture. Specifically, the command {L,L,R,R} generates a lean air-fuel mixture in the first cylinder bank (B1) during time interval t4, enabling the control unit to determine whether the first downstream lambda sensor of the first bank responds with a lean reading to the exhaust gases of lean air-fuel mixtures in the first cylinder bank. Furthermore, the command {R,R,L,L} generates a lean air-fuel mixture in the second cylinder bank (B2) during time interval t3, allowing the control unit to determine whether the downstream lambda sensor of the second bank responds with a lean reading to the exhaust gases of lean air-fuel mixtures in the second cylinder bank.

[0042] The sequence of commanded air-fuel ratios that is in Fig. As shown in Figure 3, the lambda sensor diagnostics also allow verification of whether each downstream lambda sensor is miswired. For example, the command {R,R,L,L} creates a rich air-fuel mixture in the first cylinder bank (B1) during time interval t3, enabling the control unit to detect a miswiring of the first bank's downstream lambda sensor. A properly wired first bank's downstream lambda sensor would report a rich mixture under these conditions, whereas a miswired first bank's downstream lambda sensor would report a lean mixture if the downstream lambda sensor wires were reversed. Furthermore, the command {L,L,R,R} creates a rich air-fuel mixture in the second cylinder bank (B2) during time interval t4, enabling the control unit to detect a miswiring of the second bank's downstream lambda sensor.A properly wired downstream oxygen sensor of the second bank would indicate rich during these conditions, whereas a miswired downstream oxygen sensor of the second bank would indicate lean if the downstream oxygen sensor wires are reversed.

[0043] The command {S,S,S,S} at time t0 can be used to determine reference lambda sensor responses to all stoichiometric commands. The responses of the lambda sensor assigned to the following commands at times t1, t2, t3, and t4 can be evaluated relative to the reference response at time t0. For example, if the output of the lambda sensor assigned to the first cylinder is λ = 1.02 at time t0 (e.g., due to a 2% lean fuel delivery error with open-loop control) and λ = 0.92 at time t1 (e.g., due to a 10% rich command), the relative response at time t1 can be evaluated as a rich change of λ = 0.1 (which more closely matches the rich command). In other examples, the command {S,S,S,S} at time t0 can be omitted and the response of lambda probes at times t1, t2, t3 and t4 is evaluated on an absolute basis.

[0044] It is understood that the sequence or order of air-fuel ratio commands that are in Fig. Figure 3 also influences the duration. For example, fuel commands during time intervals t1 {R,S,L,S} and t2 {S,R,S,L} are applied solely to identify miswiring of upstream oxygen sensors and may therefore have a relatively short duration (e.g., 1–3 seconds) due to relatively short exhaust gas transport delays from engine cylinders to the upstream oxygen sensors. Fuel commands during time intervals t3 {R,R,L,L} and t4 {L,L,R,R} are applied to verify whether downstream oxygen sensors respond to rich and lean commands, and therefore these commands may have a relatively longer duration (e.g., 3–5 seconds) due to the oxygen storage capacity of the catalytic converter and relatively longer exhaust gas transport delays. After time interval t3 and before time interval t4, the downstream lambda sensor of the 1stThe first cylinder bank can respond exclusively to a rich mixture after the double rich commands to P1 and P2 have sufficiently depleted the oxygen storage capacity of the first cylinder bank's catalyst. The preceding fuel commands in time intervals t1 and t2 included single rich and single stoichiometric air-fuel ratio commands (i.e., an average rich command for B1), and therefore these commands would at least partially deplete the first cylinder bank's catalyst's oxygen storage capacity before t3, thus reducing the duration required for double rich commands after time interval t3. Similarly, after time interval t3 and before time interval t4, the downstream lambda sensor of the second cylinder bank can respond exclusively to a lean mixture after the double lean commands to P3 and P4 have sufficiently saturated the second cylinder bank's catalyst's oxygen storage capacity.The preceding fuel commands in time intervals t1 and t2 included single lean and single stoichiometric air-fuel ratio commands (i.e., an average lean command for B2), and therefore the oxygen storage capacity of the second bank catalyst would be at least partially saturated before time interval t3, thus shortening the duration required for double lean commands after time interval t3. After time interval t4, the downstream lambda sensor of the first bank can respond exclusively in lean mode, since the double lean commands to P1 and P2 have sufficiently saturated the oxygen storage capacity of the first bank catalyst. The preceding double rich commands in time interval t3 would have depleted the oxygen storage capacity of the first bank catalyst and therefore increased the duration required for double lean commands after time interval t4.Similarly, after time interval t4, the downstream lambda sensor of bank 2 can react exclusively rich, after the double rich commands to P3 & P4 have sufficiently depleted the oxygen storage capacity of the second bank's catalyst. The preceding double lean commands in time interval t3 would have saturated the oxygen storage capacity of the first bank's catalyst and therefore increased the duration required for double rich commands after time interval t4. Consequently, the sequence of these sets of fuel commands affects the overall duration of the diagnostic process. It may be desirable to minimize the transitions from an average lean cylinder bank to an average rich cylinder bank, or vice versa, during successive sets of fuel commands on the same bank.Since the lambda sensor must verify that the downstream O2 sensors respond to both lean and rich commands, such a change (from average lean to average rich or vice versa) is necessary. The sequence and selection of the sets of fuel commands that are in . Fig. The 3 shown are desirable to reduce the overall time required to complete the lambda sensor diagnosis.

[0045] Now, with reference to Fig. As a second example, Table 450 is shown, illustrating a first alternative air-fuel ratio sequence for diagnosing four different upstream oxygen sensors (UEGOs). Furthermore, the air-fuel ratio sequence shown in Fig. As shown in Figure 4, this can be used to diagnose two different downstream oxygen sensors (HEGOs). Table 450 includes a first cell 402 that excludes rows 405 and 406 to indicate that these rows and their associated columns are assigned to the first bank of cylinders, B1. Table 450 also includes a second cell 404 that excludes rows 407 and 408 to indicate that these rows and their associated columns are assigned to the second bank of cylinders, B2. Table 450 includes a first column 410 that accommodates indicators for cylinder pairs (e.g.,P1 indicates the first cylinder pair (cylinders one and two), P2 the second cylinder pair (cylinders three and four), P3 the third cylinder pair (cylinders five and seven), and P4 the fourth cylinder pair (cylinders six and eight), which are assigned air-fuel ratios applied during phases of the lambda sensor diagnostic sequence shown in Table 450. The five phases of the lambda sensor diagnostic sequence are shown in columns 412-420.

[0046] The air-fuel ratio control sequence, which is in Fig. The sequence shown in 4 resembles the sequence shown in Fig. 3 is shown. However, in the sequence in Fig. 4 entries in column 320 with entries in column 318 of table 350, which are in Fig. The entries shown in figure 3 are swapped to generate table 450. The entries in Fig. 4, which are the same as entries in Fig. The three components are equivalent. Therefore, for the sake of brevity, the repetition of the description of these components is omitted.

[0047] The sequence from Fig. 4 involves two lean / rich or rich / lean transitions or switches on successive sets of air-fuel ratio commands for the same bank of cylinders. This causes an air-fuel ratio change from a catalyst state that is saturated or whose oxygen stores are depleted, which can delay the change in states of downstream oxygen sensors, thereby increasing the oxygen sensor diagnostic time. Therefore, the sequence of Fig. 4 the same functionality as the sequence from Fig. 3, however this may increase the time required to perform the lambda sensor diagnosis.

[0048] Continuing with Fig. Figure 5 shows a third example, Table 550, which illustrates a second alternative air-fuel ratio sequence for diagnosing four different upstream oxygen sensors (UEGOs). Furthermore, the air-fuel ratio sequence shown in Fig. Figure 5 is shown to be used to diagnose two different downstream oxygen sensors (HEGOs). Table 550 includes a first cell 502 that excludes rows 505 and 506 to indicate that these rows and their associated columns are assigned to the first bank of cylinders, B1. Table 550 also includes a second cell 504 that excludes rows 507 and 508 to indicate that these rows and their associated columns are assigned to the second bank of cylinders, B2. Table 550 includes a first column 510 that accommodates indicators for cylinder pairs (e.g.,P1 indicates the first cylinder pair (cylinders one and two), P2 the second cylinder pair (cylinders three and four), P3 the third cylinder pair (cylinders five and seven), and P4 the fourth cylinder pair (cylinders six and eight), which are assigned air-fuel ratios applied during phases of the lambda sensor diagnostic sequence shown in Table 550. The five phases of the lambda sensor diagnostic sequence are shown in columns 512–520.

[0049] The air-fuel ratio control sequence, which is in Fig. The sequence shown in 5 resembles the sequence shown in Fig. 3 is shown. However, in the sequence in Fig. 5 column entries swapped. The entries in Fig. 5, which are the same as entries in Fig. The three components are equivalent. Therefore, for the sake of brevity, the repetition of the description of these components is omitted.

[0050] The sequence from Fig. 5 increases the actual total number of lean / rich or rich / lean transitions or switches on successive sets of air-fuel ratio commands for the same bank of cylinders. This causes an air-fuel ratio change from a catalyst state that is saturated or whose oxygen stores are depleted, which can delay the change in states of downstream oxygen sensors, thereby increasing the oxygen sensor diagnostic time. Therefore, the sequence of Fig. 5 the same functionality as the sequence from Fig. 3, however this may increase the time required to perform the lambda sensor diagnosis.

[0051] Now, with reference to Fig. 6 A fourth example is shown in Table 650, which illustrates a third alternative air-fuel ratio sequence for diagnosing four different upstream oxygen sensors (UEGOs). The air-fuel ratio sequence shown in Fig. As shown in Figure 6, this can also be used to diagnose two different downstream oxygen sensors (HEGOs). Table 650 includes a first cell 602 that excludes rows 605 and 606 to indicate that these rows and their associated columns are assigned to the first bank of cylinders, B1. Table 650 also includes a second cell 604 that excludes rows 607 and 608 to indicate that these rows and their associated columns are assigned to the second bank of cylinders, B2. Table 650 includes a first column 610 that accommodates indicators for cylinder pairs (e.g.,P1 indicates the first cylinder pair (cylinders one and two), P2 the second cylinder pair (cylinders three and four), P3 the third cylinder pair (cylinders five and seven), and P4 the fourth cylinder pair (cylinders six and eight), which are assigned air-fuel ratios applied during phases of the lambda sensor diagnostic sequence shown in Table 650. The five phases of the lambda sensor diagnostic sequence are shown in columns 612–620.

[0052] The air-fuel ratio control sequence, which is in Fig. The sequence shown in 6 resembles the sequence shown in Fig. 3 is shown. However, in the sequence in Fig. Six column entries were swapped. The entries in Fig. 6, which are the same as entries in Fig. The three components are equivalent. Therefore, for the sake of brevity, the repetition of the description of these components is omitted.

[0053] The sequence from Fig. 6 represents the actual total number of lean / rich or rich / lean transitions or switches on successive sets of air-fuel ratio commands for the same bank of cylinders. Therefore, the sequence of Fig. 6 the same functionality as the sequence from Fig. 3 provide and reduce the time required to perform the lambda sensor diagnosis (compared to the sequences from Fig. 4 and Fig. 5).

[0054] Now, with reference to Fig. 7 A fifth example is shown in Table 750, illustrating a third alternative air-fuel ratio sequence for diagnosing four different upstream oxygen sensors (UEGOs). The air-fuel ratio sequence shown in Fig. As shown in Figure 7, this can also be used to diagnose two different downstream oxygen sensors (HEGOs). Table 750 includes a first cell 702 that excludes rows 705 and 706 to indicate that these rows and their associated columns are assigned to the first bank of cylinders, B1. Table 750 also includes a second cell 704 that excludes rows 707 and 708 to indicate that these rows and their associated columns are assigned to the second bank of cylinders, B2. Table 750 includes a first column 710 that accommodates indicators for cylinder pairs (e.g.,P1 indicates the first cylinder pair (cylinders one and two), P2 the second cylinder pair (cylinders three and four), P3 the third cylinder pair (cylinders five and seven), and P4 the fourth cylinder pair (cylinders six and eight), which are assigned air-fuel ratios applied during phases of the lambda sensor diagnostic sequence shown in Table 750. The five phases of the lambda sensor diagnostic sequence are shown in columns 712-720.

[0055] The air-fuel ratio control sequence, which is in Fig. The sequence shown in 7 resembles the sequence shown in Fig. 3 is shown. However, in the sequence in Fig. 7 column entries swapped. The entries in Fig. 7, which are the same as entries in Fig. The three components are equivalent. Therefore, for the sake of brevity, the repetition of the description of these components is omitted.

[0056] The sequence from Fig. 7 represents the actual total number of lean / rich or rich / lean transitions or switches on successive sets of air-fuel ratio commands for the same bank of cylinders. Therefore, the sequence of Fig. 7 the same functionality as the sequence from Fig. 3 provide and reduce the time required to perform the lambda sensor diagnosis (compared to the sequences from Fig. 4 and Fig. 5).

[0057] Now, with reference to Fig. 8 a method 800 for operating an engine and diagnosing a lambda sensor cylinder imbalance is shown. The method from Fig. 8 can be entered into the system as executable instructions stored in non-transient memory. Fig. 1 and Fig. 2 be integrated. The procedure from Fig. 8 can be in Fig. The control unit shown in section 1 is to be caused to receive inputs from one or more sensors described in this document and to set the positions or operating states of one or more actuators described in this document in the physical world. Procedure 800 can be executed while the engine is running and burning fuel.

[0058] At 802, procedure 800 assesses whether or not to enable oxygen diagnostics. If procedure 800 assesses that oxygen diagnostics should be enabled, the answer is yes, and procedure 800 proceeds to 804. Otherwise, the answer is no, and procedure 800 terminates. In an example, procedure 800 might enable oxygen diagnostics during selected vehicle operating conditions, which could include one or more of the following: a diagnostic request at the end of the assembly line, a certain amount of time elapsed since the last oxygen diagnostic was performed, a request for a diagnostic tool, and unexpected oxygen sensor behavior.

[0059] In 804, the procedure 800 disrupts the air-fuel ratios of the cylinders of two cylinder banks according to the air-fuel sequences that are defined in one of Fig. Figures 3-7, or subsets thereof, are shown. Thus, Method 800 can involve at least four distinct air-fuel ratio patterns, but fewer than six distinct air-fuel ratio patterns, in two pairs of cylinders during at least four distinct time intervals of a lambda sensor diagnosis. The air-fuel sequences of the cylinders and cylinder banks can be arranged in a sequence to reduce the execution time of the lambda sensor diagnosis. For example, the air-fuel ratio changes can be arranged to reduce repeated filling and depletion of oxygen from catalysts, so that operating states of downstream lambda sensors generated in response to air-fuel ratios in a cylinder can be determined with less delay. Method 800 transitions to 806.

[0060] In the 806, procedure 800 determines whether upstream lambda sensors respond correctly to changes in the air-fuel ratios in a cylinder. For example, and how in relation to Fig. As discussed in section 3, if procedure 800 issues a command for a rich air-fuel ratio to a cylinder pair and an upstream oxygen sensor assigned to that cylinder pair indicates rich exhaust gases at a control input, it can be determined that the upstream oxygen sensor assigned to that cylinder pair responds to burnt rich air-fuel mixtures. In this way, oxygen sensor outputs can be compared with table entries to determine whether an oxygen sensor may be worn. If the upstream oxygen sensor assigned to the cylinder indicates lean or stoichiometric exhaust gases, procedure 800 can determine that the upstream oxygen sensor assigned to that cylinder pair does not respond to rich exhaust gases.The upstream oxygen sensors can be evaluated to determine whether they are capable of responding to lean exhaust gases produced from lean air-fuel mixtures, similarly by instructing the cylinder to burn lean air-fuel mixtures and assessing whether the oxygen sensor assigned to that cylinder pair responds to lean exhaust gases. Oxygen sensors for each cylinder pair can be evaluated similarly when the cylinder's air-fuel ratios are set according to the air-fuel sequences from step 804. Procedure 800 proceeds to 808.

[0061] In procedure 808, procedure 800 determines whether upstream oxygen sensors are miswired. For example, procedure 800 can determine whether an output of upstream oxygen sensor number one is correctly wired to the control input associated with the first upstream oxygen sensor or upstream oxygen sensor number one, or is miswired to some other control input. Thus, if procedure 800 issues a rich air-fuel ratio command to a pair of cylinders, and a first upstream oxygen sensor associated with a first pair of cylinders indicates rich exhaust gases, it can be determined that the first upstream oxygen sensor associated with that pair of cylinders is correctly wired.However, if the control input associated with the first upstream oxygen sensor outputs a lean or stoichiometric signal, and a control input associated with another upstream oxygen sensor switches to indicate a rich mixture, Method 800 can determine that the first upstream oxygen sensor is miswired to the control system. In this way, oxygen sensor outputs can be compared with table entries and / or air-fuel ratio changes between table entries to determine whether an oxygen sensor is wired correctly. Method 800 can perform an additional similar analysis for each of the upstream oxygen sensors.

[0062] At 810, procedure 800 determines whether downstream oxygen sensors are responding correctly to changes in the air-fuel ratios in a cylinder and whether the downstream oxygen sensors are wired correctly. In an example, and as with respect to Fig. As discussed in section 3, Method 800 can command two pairs of cylinders or a cylinder bank to burn rich air-fuel mixtures. It can be determined that the downstream oxygen sensor assigned to the cylinder bank responds to burned rich air-fuel mixtures if the downstream oxygen sensor indicates rich exhaust gases at a control input assigned to the downstream oxygen sensor. If the downstream oxygen sensor assigned to the cylinder bank indicates rich exhaust gases, Method 800 can determine that the downstream oxygen sensor assigned to the cylinder bank responds to rich exhaust gases. However, if the downstream lambda sensor assigned to the cylinder bank indicates lean or stoichiometric exhaust gases, the procedure 800 can determine that the downstream lambda sensor assigned to the cylinder bank does not respond to rich exhaust gases.Furthermore, if the control input assigned to the downstream oxygen sensor does not indicate a rich mixture, and another control input switches to a rich mixture, the procedure 800 can determine that the downstream oxygen sensor assigned to the first cylinder bank is miswired. Both downstream oxygen sensors can be evaluated in this way. The procedure 800 then proceeds to 812.

[0063] In the case of 812, the procedure can be used to identify 800 lambda sensors that do not react as expected or that are determined to be miswired, on a human-machine interface (e.g., 171 from Fig. 1) display. Furthermore, Procedure 800 may perform mitigating measures. Mitigating measures may include, among other things, adjustments to engine fuel commands and control modifications. For example, if Procedure 800 determines that the downstream oxygen sensor of the first bank is wired to the control input for the downstream oxygen sensor of the second bank, the control unit may adjust the fuel supply to the first bank of cylinders according to the control input that should be assigned to the downstream oxygen sensor of the second bank of cylinders. Furthermore, the control unit may adjust the fuel supply to the second bank of cylinders according to the control input that should be assigned to the downstream oxygen sensor of the first bank of cylinders.If an upstream oxygen sensor does not respond to a pair of cylinders for which a rich or lean mixture has been commanded, the air-fuel ratios of the cylinders assigned to the unresponding oxygen sensor can be controlled in response to an output from another upstream oxygen sensor. In this way, it may be possible to maintain some degree of control over engine cylinders assigned to an unresponding upstream oxygen sensor. Procedure 800 proceeds to the end.

[0064] In this way, the operation of multiple upstream oxygen sensors can be diagnosed simultaneously with a diagnostic operation of downstream oxygen sensors. Furthermore, the air-fuel ratio command sequences described herein provide the identification of specific oxygen sensors for wear and / or proper operation. Additionally, the air-fuel ratio commands described herein provide a reduction in the time required to diagnose both upstream and downstream oxygen sensors.

[0065] The procedure from Fig. Document 8 provides a method for operating an engine, comprising: issuing a command to each of two sets of fuel injectors to produce a stoichiometric, rich, or lean air-fuel ratio in each of two pairs of cylinders, and generating at least four distinct air-fuel ratio patterns of the cylinders in the two pairs of cylinders during at least four distinct time intervals of lambda sensor diagnostics. In a first example, the method further comprises comparing outputs from two upstream lambda sensors with the at least four distinct air-fuel ratio patterns of the cylinders and identifying the presence or absence of a wiring fault from each of the two upstream lambda sensors.In a second example, which may include the first example, the method further comprises comparing outputs from two upstream oxygen sensors with the at least four different air-fuel ratio patterns of the cylinders and identifying the presence or absence of wear on each of the two upstream oxygen sensors. In a third example, which may include one or both of the first and second examples, the method further comprises comparing outputs from a downstream oxygen sensor with the at least four different air-fuel ratio patterns of the cylinders and identifying the presence or absence of miswiring of the downstream oxygen sensor.In a fourth example, which may include one or more of the first three examples, the method further comprises comparing outputs from downstream oxygen sensors with the at least four distinct air-fuel ratio patterns of the cylinders and identifying the presence or absence of wear on the downstream oxygen sensors. In a fifth example, which may include one or more of the first four examples, the method comprises sequencing the at least four distinct air-fuel ratio patterns of the cylinders to reduce the time required to perform the oxygen sensor diagnostics.In a sixth example, which may include one or more of the first to fifth examples, the method comprises issuing a command to each of two other groups of fuel injectors to produce one of the stoichiometric, rich or lean air-fuel ratio patterns in each of two other pairs of cylinders and to produce a second group of at least four different air-fuel ratio patterns of the cylinders in the other two pairs of cylinders during the at least four different time intervals of lambda sensor diagnostics.In a seventh example, which may include one or more of the first to sixth examples, the method further comprises comparing outputs from downstream lambda sensors with the second group of at least four different air-fuel ratio patterns of the cylinders and identifying the presence or absence of wear on the downstream lambda sensors.

[0066] The procedure from Fig.Section 8 further provides a method for operating an engine, comprising: issuing a command to a maximum of one air-fuel ratio change from rich to lean or from lean to rich in a pair of engine cylinders during a lambda sensor diagnostic sequence, which is a basis for determining a miswiring of four upstream lambda sensors, and comparing outputs from the four upstream lambda sensors with air-fuel ratio changes made during the lambda sensor diagnostic sequence. In a first example, the method includes the lambda sensor diagnostic sequence including at least four different air-fuel ratio patterns of the cylinders. In a second example, which may include the first example, the method further includes comparing outputs from the four upstream lambda sensors with the at least four different air-fuel ratio patterns of the cylinders.In a third example, which may include one or both of the first and second examples, the method further comprises indicating wear from one of the four upstream oxygen sensors in response to a difference between the at least four distinct air-fuel ratio patterns of the cylinders and an output from one of the four upstream oxygen sensors. In a fourth example, which may include one or more of the first through third examples, the method comprises issuing a command to a maximum of one air-fuel ratio change from rich to lean or from lean to rich, which involves adjusting a fuel injection device operation.

[0067] It should be noted that the exemplary control and estimation routines contained in this document can be used with various engine and / or vehicle system configurations. The control procedures and routines disclosed herein can be stored as executable instructions in non-transitory memory and can be executed by the control system, in combination with the various sensors, actuators, and other engine hardware. The specific routines described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Therefore, various illustrated actions, operations, and / or functions can be performed in the illustrated sequence or in parallel, or in some cases, omitted.Likewise, the processing sequence is not strictly necessary to achieve the features and benefits of the examples described in this document, but is provided for the sake of clarity and description. One or more of the illustrated actions, processes, and / or functions can be performed repeatedly, depending on the specific strategy employed. Furthermore, the described actions, processes, and / or functions can graphically represent code to be programmed into non-transient memory of the computer-readable storage medium within the engine control system, with the described actions being executed by carrying out the instructions in a system that includes the various engine hardware components in combination with the electronic control unit.

[0068] This concludes the description. A person skilled in the art would notice many changes and modifications upon reading it, without altering the essence and scope of the description. For example, I3, I4, I5, V6, V8, V10, and V12 engines operating in natural gas, gasoline, diesel, or alternative fuel configurations could benefit from this description.

[0069] According to the present invention, a method for operating an engine comprises: issuing a command to each of two groups of fuel injection devices to generate a stoichiometric, rich or lean air-fuel ratio in each of two pairs of cylinders and to generate at least four different air-fuel ratio patterns of the cylinders in the two pairs of cylinders during at least four different time intervals of a lambda sensor diagnosis.

[0070] In one aspect of the invention, the method involves comparing outputs from two upstream lambda sensors with the at least four different air-fuel ratio patterns of the cylinders and identifying the presence or absence of a miswiring of each of the two upstream lambda sensors.

[0071] In a first example, the procedure further includes comparing outputs from two upstream lambda sensors with the at least four different air-fuel ratio patterns of the cylinders and identifying the presence or absence of wear from each of the two upstream lambda sensors.

[0072] In one aspect of the invention, the method involves comparing outputs of a downstream lambda sensor with the at least four different air-fuel ratio patterns of the cylinders and identifying the presence or absence of a miswiring of the downstream lambda sensor.

[0073] In one aspect of the invention, the method involves comparing outputs from downstream lambda sensors with the at least four different air-fuel ratio patterns of the cylinders and identifying the presence or absence of wear on the downstream lambda sensors.

[0074] In one aspect of the invention, the at least four different air-fuel ratio patterns of the cylinders are arranged in a sequence to reduce the amount of time required to perform the lambda sensor diagnosis.

[0075] In one aspect of the invention, the method involves issuing a command to each of two other groups of fuel injection devices to generate one of the stoichiometric, rich or lean air-fuel ratio patterns in each of two other pairs of cylinders and to generate a second group of at least four different air-fuel ratio patterns of the cylinders in the other two pairs of cylinders during the at least four different time intervals of the lambda sensor diagnosis.

[0076] In one aspect of the invention, the method involves comparing outputs from downstream lambda sensors with the second group of at least four different air-fuel ratio patterns of the cylinders and identifying the presence or absence of wear on the downstream lambda sensors.

[0077] According to the present invention, an engine system is provided comprising: an internal combustion engine comprising a first bank of cylinders and a second bank of cylinders, and at least eight fuel injection devices, comprising at least one fuel injection device for each cylinder of the first bank of cylinders and at least one fuel injection device for each cylinder of the second bank; a first lambda sensor configured to detect gases discharged from a first and a second cylinder of the first bank of cylinders; a second lambda sensor configured to detect gases discharged from a third and a fourth cylinder of the first bank of cylinders; a third lambda sensor configured to detect gases discharged from a fifth and a sixth cylinder of the second bank of cylinders;a fourth lambda sensor configured to detect gases discharged from a seventh and an eighth cylinder of the second bank of cylinders; a controller comprising executable instructions stored in non-transient memory that cause the controller to command the at least eight fuel injectors to perform one of a stoichiometric, rich or lean air-fuel ratio in each cylinder of the first bank of cylinders and each cylinder of the second bank, and to produce at least four different air-fuel ratio patterns of the cylinders in the first bank of cylinders and the second bank of cylinders during at least four different time intervals of a lambda sensor diagnostic sequence.

[0078] According to one embodiment, the at least four different air-fuel ratio patterns of the cylinders are arranged in a sequence to reduce the duration of the lambda sensor diagnostic sequence.

[0079] According to one embodiment, the invention is further characterized by additional executable instructions that cause the control unit to compare outputs from the first lambda sensor, the second lambda sensor, the third lambda sensor and the fourth lambda sensor with the at least four different air-fuel ratio patterns of the cylinders and to identify the presence or absence of a miswiring of each of the first lambda sensor, the second lambda sensor, the third lambda sensor and the fourth lambda sensor.

[0080] According to one embodiment, the invention is further characterized by additional executable instructions that cause the control system to compare outputs from the first lambda sensor, the second lambda sensor, the third lambda sensor and the fourth lambda sensor with the at least four different air-fuel ratio patterns of the cylinders and to identify the presence or absence of wear from each of the first lambda sensor, the second lambda sensor, the third lambda sensor and the fourth lambda sensor.

[0081] According to one embodiment, the invention is further characterized by a first downstream lambda sensor arranged in a fifth exhaust passage, and comparisons of outputs of the first downstream lambda sensor with the at least four different air-fuel ratio patterns of the cylinders and additional executable instructions for identifying the presence or absence of a miswiring of the first downstream lambda sensor.

[0082] According to one embodiment, the invention is further characterized by a second downstream lambda sensor arranged in a sixth exhaust passage, and additional executable instructions for comparing outputs of the second downstream lambda sensor with the at least four different air-fuel ratio patterns of the cylinders and identifying the presence or absence of a miswiring of the second downstream lambda sensor.

[0083] According to one embodiment, the invention is further characterized by additional executable instructions that cause the control system to indicate the presence or absence of wear of each of the first downstream lambda probe and the second downstream lambda probe.

[0084] According to the present invention, a method for operating an engine comprises: issuing a command to a maximum of one air-fuel ratio change from rich to lean or from lean to rich in a pair of engine cylinders during a lambda sensor diagnostic sequence, which is a basis for determining a miswiring of four upstream lambda sensors, and comparing outputs of the four upstream lambda sensors with air-fuel ratio changes performed during the lambda sensor diagnostic sequence.

[0085] In one aspect of the invention, the method includes the lambda sensor diagnostic sequence comprising at least four different air-fuel ratio patterns of the cylinders.

[0086] In one aspect of the invention, the method further involves comparing outputs from the four upstream lambda sensors with the at least four different air-fuel ratio patterns of the cylinders.

[0087] In one aspect of the invention, the method involves indicating wear from one of the four upstream lambda sensors in response to a difference between the at least four different air-fuel ratio patterns of the cylinders and an output from one of the four upstream lambda sensors.

[0088] In one aspect of the invention, issuing a command to change the air-fuel ratio by a maximum of one change from rich to lean or from lean to rich involves adjusting the operation of a fuel injection device.

Claims

[1] Method for operating an engine comprising: Issuing a command to each of two groups of fuel injection devices to generate a stoichiometric, rich or lean air-fuel ratio in each of two pairs of cylinders and to generate at least four different air-fuel ratio patterns of the cylinders in the two pairs of cylinders during at least four different time intervals of a lambda sensor diagnosis. [2] Method according to claim 1, further comprising comparing outputs from two upstream lambda sensors with the at least four different air-fuel ratio patterns of the cylinders and identifying the presence or absence of a miswiring of each of the two upstream lambda sensors. [3] Method according to claim 1, further comprising comparing outputs from two upstream lambda sensors with the at least four different air-fuel ratio patterns of the cylinders and identifying the presence or absence of wear on each of the two upstream lambda sensors. [4] Method according to claim 1, further comprising comparing outputs of a downstream lambda sensor with the at least four different air-fuel ratio patterns of the cylinders and identifying the presence or absence of a miswiring of the downstream lambda sensor. [5] Method according to claim 1, further comprising comparing outputs from downstream lambda sensors with the at least four different air-fuel ratio patterns of the cylinders and identifying the presence or absence of wear of the downstream lambda sensors. [6] Method according to claim 1, wherein the at least four different air-fuel ratio patterns of the cylinders are arranged in a sequence to reduce the amount of time required to perform the lambda sensor diagnosis. [7] Method according to claim 1, further comprising issuing a command to each of two other groups of fuel injection devices to generate one of the stoichiometric, rich or lean air-fuel ratio patterns in each of two other pairs of cylinders and to generate a second group of at least four different air-fuel ratio patterns of the cylinders in the other two pairs of cylinders during the at least four different time intervals of the lambda sensor diagnosis. [8] Method according to claim 7, further comprising comparing outputs from downstream lambda sensors with the second group of at least four different air-fuel ratio patterns of the cylinders and identifying the presence or absence of wear of the downstream lambda sensors. [9] Engine system comprising the following: an internal combustion engine comprising a first bank of cylinders and a second bank of cylinders and at least eight fuel injection devices, including at least one fuel injection device for each cylinder of the first bank of cylinders and at least one fuel injection device for each cylinder of the second bank; a first lambda sensor configured to detect gases discharged from a first and a second cylinder of the first bank of cylinders; a second lambda sensor configured to detect gases discharged from a third and a fourth cylinder of the first bank of cylinders; a third lambda sensor configured to detect gases discharged from a fifth and a sixth cylinder of the second bank of cylinders; a fourth lambda sensor configured to detect gases discharged from a seventh and an eighth cylinder of the second bank of cylinders; a controller comprising executable instructions stored in non-transitory memory that cause the controller to issue a command to the at least eight fuel injectors to produce one of a stoichiometric, rich or lean air-fuel ratio in each cylinder of the first bank of cylinders and each cylinder of the second bank, and to produce at least four different air-fuel ratio patterns of the cylinders in the first bank of cylinders and the second bank of cylinders during at least four different time intervals of a lambda sensor diagnostic sequence. [10] Engine system according to claim 9, wherein the at least four different air-fuel ratio patterns of the cylinders are arranged in a sequence to reduce the duration of the lambda sensor diagnostic sequence. [11] Engine system according to claim 9, further comprising additional executable instructions that cause the control to compare outputs from the first lambda sensor, the second lambda sensor, the third lambda sensor and the fourth lambda sensor with the at least four different air-fuel ratio patterns of the cylinders and to identify the presence or absence of a miswiring of each of the first lambda sensor, the second lambda sensor, the third lambda sensor and the fourth lambda sensor. [12] Engine system according to claim 9, further comprising additional executable instructions that cause the control to compare outputs from the first lambda sensor, the second lambda sensor, the third lambda sensor and the fourth lambda sensor with the at least four different air-fuel ratio patterns of the cylinders and to identify the presence or absence of wear of each of the first lambda sensor, the second lambda sensor, the third lambda sensor and the fourth lambda sensor. [13] Engine system according to claim 12, further comprising a first downstream lambda sensor arranged in a fifth exhaust passage, and comparing outputs of the first downstream lambda sensor with the at least four different air-fuel ratio patterns of the cylinders and additional executable instructions for identifying the presence or absence of a miswiring of the first downstream lambda sensor. [14] Engine system according to claim 13, further comprising a second downstream lambda sensor arranged in a sixth exhaust passage, and additional executable instructions for comparing outputs of the second downstream lambda sensor with the at least four different air-fuel ratio patterns of the cylinders and identifying the presence or absence of a miswiring of the second downstream lambda sensor. [15] Motor system according to claim 14, further comprising additional executable instructions that cause the control system to indicate the presence or absence of wear of each of the first downstream lambda sensor and the second downstream lambda sensor.

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