System and method for diagnosing nox sensor based on ammonia slip

Abstract

A method for diagnosing a NOx sensor is provided. The method includes receiving data indicative of operating conditions of an engine or aftertreatment system; determining that an amount of NOx output from the aftertreatment system during a first time period satisfies a low NOx operating mode condition; determining, based on the data regarding operation of the aftertreatment system, that there is an operating condition regarding ammonia slip during a second time period; in response to determining that there is the operating condition regarding ammonia slip, determining that the amount of NOx output from the aftertreatment system satisfies a high NOx operating mode condition; comparing a difference between a minimum value from the first time period and a maximum value from the second time period to a diagnostic threshold; and in response to the difference being less than the diagnostic threshold, setting an alert.

Description

[0001] Cross-references

[0002] This application claims priority and benefit to U.S. Application No. 63 / 031,922, filed May 29, 2020, entitled “SYSTEMS AND METHODS FOR DIAGNOSINGNOx SENSOR BASED ON AMMONIA SLIP,” which is incorporated herein by reference in its entirety and for all purposes. Technical Field

[0003] This disclosure relates to the diagnosis and prediction of exhaust aftertreatment systems. Background Technology

[0004] Exhaust aftertreatment systems are typically designed to reduce emissions of particulate matter, nitrogen oxides (NOx), hydrocarbons, and other environmentally harmful pollutants. However, components that make up an exhaust aftertreatment system can be prone to failure and degradation. Because component failure or degradation can have adverse consequences for the performance of the exhaust aftertreatment system and its ability to reduce emissions, it is desirable to detect and, where possible, correct failed or degraded components. Most regulations require on-board diagnostic (OBD) monitoring or testing of many components of an exhaust aftertreatment system. When installed in a vehicle, most monitoring and testing of aftertreatment system components is performed during on-road operation (e.g., while the vehicle is traveling on a road). While this monitoring and testing may be convenient, its effectiveness can be limited because the engine cannot operate outside the given on-road calibration operating range. Furthermore, since on-road operation requirements often take precedence over diagnostic and performance recovery procedures, the sequence, timing, and control of these procedures may be less than ideal. Consequently, the detection and correction of various failure modes in the exhaust aftertreatment system may be limited. Summary of the Invention

[0005] One embodiment relates to a system comprising: a controller comprising at least one processor coupled to a memory storing instructions that, when executed by the at least one processor, cause the controller to perform operations comprising: receiving data indicative of an operating condition of at least one of an engine or an aftertreatment system; determining, based on an analysis of the data indicative of the operating condition, that an amount of NOx output from the aftertreatment system during a first time period satisfies a low NOx operating mode condition; determining, based on data regarding operation of the aftertreatment system, that there is an operating condition regarding ammonia slip during a second time period; in response to determining that there is the operating condition regarding ammonia slip, determining that the amount of NOx output from the aftertreatment system satisfies a high NOx operating mode condition; taking a minimum of the amount of NOx output from the aftertreatment system during the first time period; taking a maximum of the amount of NOx output from the aftertreatment system during the second time period; comparing a difference between the minimum and the maximum to a diagnostic threshold; and in response to the difference being less than the diagnostic threshold, setting an alert.

[0006] In some implementations, the data regarding operation of the aftertreatment system includes a temperature change rate of a SCR catalyst in the aftertreatment system or an amount of ammonia storage in the aftertreatment system.

[0007] In some implementations, determining that the amount of NOx output from the aftertreatment system satisfies the low NOx operating mode condition includes at least one of determining that a fueling level of the engine is below a fueling threshold, determining that a temperature of a selective catalytic reduction (SCR) catalyst in the aftertreatment system is at or above a temperature threshold, or determining that an amount of ammonia slip is below an ammonia threshold.

[0008] In some implementations, the minimum is taken in response to the first time period exceeding a time threshold.

[0009] In some implementations, determining that there is the operating condition regarding ammonia slip includes at least one of determining the amount of ammonia slip or determining that a conversion efficiency of a selective catalytic reduction (SCR) catalyst in the aftertreatment system is below an efficiency threshold.

[0010] In some implementations, the maximum is taken in response to the second time period exceeding a time threshold.

[0011] In some implementations, the system further changes, in response to the difference being less than the diagnostic threshold, a closed loop feedback loop utilizing both an exhaust sensor at a system output end and an exhaust sensor at an engine output end to an open loop feedback loop utilizing the exhaust sensor at the engine output end.

[0012] Another embodiment relates to a method for diagnosing a NOx sensor. The method includes receiving data indicative of an operating condition of at least one of an engine or an aftertreatment system; determining, based on the data indicative of the operating condition, that an amount of NOx output from the aftertreatment system during a first time period satisfies a low NOx operating mode condition; determining, based on data regarding operation of the aftertreatment system, that there is an operating condition regarding ammonia slip during a second time period; in response to determining that there is the operating condition regarding ammonia slip, determining that the amount of NOx output from the aftertreatment system satisfies a high NOx operating mode condition; taking a minimum of the amount of NOx output from the aftertreatment system during the first time period; taking a maximum of the amount of NOx output from the aftertreatment system during the second time period; comparing a difference between the minimum and the maximum to a diagnostic threshold; and in response to the difference being less than the diagnostic threshold, setting an alert regarding the NOx sensor.

[0013] In some implementations, the data regarding operation of the aftertreatment system includes a temperature change rate of a SCR catalyst in the aftertreatment system or an amount of ammonia storage in the aftertreatment system.

[0014] In some implementations, determining that the amount of NOx output from the aftertreatment system satisfies the low NOx operating mode condition includes at least one of determining that a fueling level of the engine is below a fueling threshold, determining that a temperature of a selective catalytic reduction (SCR) catalyst in the aftertreatment system is at or above a temperature threshold, or determining that an amount of ammonia slip is below an ammonia threshold.

[0015] In some implementations, the minimum is taken in response to the first time period exceeding a time threshold.

[0016] In some implementations, determining that there is the operating condition regarding ammonia slip includes at least one of determining an amount of ammonia slip or determining that a conversion efficiency of a selective catalytic reduction (SCR) catalyst in the aftertreatment system is below an efficiency threshold.

[0017] In some implementations, the maximum is taken in response to the second time period exceeding a time threshold.

[0018] In some implementations, the method further changes, in response to the difference being less than the diagnostic threshold, a closed-loop feedback loop utilizing both an exhaust sensor at a system output end and an exhaust sensor at an engine output end to an open-loop feedback loop utilizing the exhaust sensor at the engine output end.

[0019] Another embodiment relates to a system comprising: an aftertreatment system in exhaust receiving communication with an engine; and a controller coupled to the aftertreatment system and the engine, the controller configured to: receive data indicative of an operating condition of at least one of the engine or the aftertreatment system; determine, based on the data indicative of the operating condition, that an amount of NOx output from the aftertreatment system during a first time period satisfies a low NOx operating mode condition; determine, based on data regarding operation of the aftertreatment system, that there is an operating condition regarding ammonia slip during a second time period; in response to determining that there is the operating condition regarding ammonia slip, determine that the amount of NOx output from the aftertreatment system satisfies a high NOx operating mode condition; take a minimum of the amount of NOx output from the aftertreatment system during the first time period; take a maximum of the amount of NOx output from the aftertreatment system during the second time period; compare a difference between the minimum and the maximum to a diagnostic threshold; and in response to the difference being less than the diagnostic threshold, set an alert.

[0020] In some implementations, determining that the amount of NOx output from the aftertreatment system satisfies the low NOx operating mode condition comprises at least one of: determining that a fueling level of the engine is below a fueling threshold, determining that a temperature of a selective catalytic reduction (SCR) catalyst in the aftertreatment system is at or above a temperature threshold, or determining that an amount of ammonia slip is below an ammonia threshold.

[0021] In some implementations, the minimum is taken during the first time period in response to the first time period exceeding a time threshold.

[0022] In some implementations, determining that there is the operating condition regarding ammonia slip comprises at least one of: determining the amount of ammonia slip or determining that a conversion efficiency of a selective catalytic reduction (SCR) catalyst in the aftertreatment system is below an efficiency threshold.

[0023] In some implementations, the maximum is taken during the second time period in response to the second time period exceeding a time threshold.

[0024] In some implementations, the system further changes, in response to the difference being less than the diagnostic threshold, a closed loop feedback loop utilizing both an exhaust sensor at a system output and an exhaust sensor at an engine output to an open loop feedback loop utilizing the exhaust sensor at the engine output.

[0025] This Summary is an overview of some example embodiments and is not intended to be limiting in any way. In conjunction with the drawings and detailed description set forth below, other aspects, implementations, and advantages of the devices or processes described herein will become apparent to those of ordinary skill in the art, and the devices or processes described herein can be put to use with departures from the embodiments set forth in this Summary and in the drawings and detailed description, which are to be considered as illustrative and not restrictive. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a schematic diagram of an engine system in accordance with example embodiments.

[0027] Figure 2 is a method for diagnosing a system-out NOx sensor according to example embodiments Figure 1 schematic diagram of a controller of an engine system.

[0028] Figure 3 is a flowchart of a method for diagnosing a system-out NOx sensor according to example embodiments. DETAILED DESCRIPTION

[0029] The following is a more detailed description of various concepts related to methods, apparatuses, and systems for diagnosing a system-out NOx sensor based in part on conditions indicative of high ammonia slip. Before turning to the figures, which illustrate certain example embodiments in detail, it should be understood that the present disclosure is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology used herein is for the purpose of description only and should not be considered limiting.

[0030] With general reference to the figures, various embodiments disclosed herein relate to systems, apparatuses, and methods for diagnosing a NOx sensor in an exhaust aftertreatment system. According to the present disclosure, a controller includes at least one processor coupled to a memory storing instructions that, when executed by the at least one processor, cause the at least one processor to: receive data indicative of operating conditions of an engine and an aftertreatment system; determine, based on analysis of the data indicative of operating conditions, that an amount of NOx output from the aftertreatment system during a first time period is low; determine, based on analysis of the data indicative of operating conditions, that an amount of NOx output from the aftertreatment system during a second time period is high; take a minimum of the amount of NOx output from the aftertreatment system during the first time period; take a maximum of the amount of NOx output from the aftertreatment system during the second time period; compare a difference between the minimum and the maximum to a diagnostic threshold, and in response to the difference being less than the diagnostic threshold, set an alert.

[0031] As a brief overview, some engine systems include exhaust aftertreatment systems for reducing pollutants emitted from the engine system. Among other components, these exhaust aftertreatment systems can include a selective catalytic reduction (SCR) system. The SCR system includes an SCR catalyst designed to reduce nitrogen oxides (NOx) in the engine exhaust to nitrogen and other less harmful compounds. To achieve this reduction, a reductant is injected into the exhaust stream before the exhaust reaches the SCR system. As the exhaust stream passes through the SCR catalyst, the NOx reacts with ammonia formed from the reductant decomposition to form nitrogen and other less harmful compounds. Accordingly, a reduction in NOx emissions from the exhaust is achieved. The efficiency of the SCR catalyst can be determined by measuring the amount of NOx emissions remaining in the exhaust at the outlet of the SCR system or at another point, such as a system output location.

[0032] Because the measured value of the amount of NOx emissions remaining in the exhaust at the outlet of the SCR system (i.e., system output NOx) is a primary indicator of the efficacy of the SCR system, if the system output NOx sensor (also referred to as a tailpipe NOx sensor) is degraded or "stuck," the system output NOx sensor is no longer sufficiently reliable to effectively determine the efficacy of the SCR system because the system output NOx sensor is not properly sensing the amount of NOx in the exhaust or is too slow to react to changes in the amount of NOx in the exhaust. Moreover, in those systems where reductant dosing is tied to the system output NOx sensor, if the system output NOx sensor is stuck, control of the reductant dosing is compromised.

[0033] According to the present disclosure, the controller continuously samples output data from the system output NOx sensor. Based on internal and external operating conditions, if the controller determines that the engine is producing a relative extreme of NOx (e.g., producing a relatively high amount of NOx), the controller analyzes the continuously sampled data. For example, if the operating conditions are such that the controller determines that the engine is producing a relatively high amount of NOx (e.g., high DEF dosing levels, low SCR catalyst temperature, etc.), the controller examines the continuously sampled data in order to identify the maximum sensed value during high NOx production. Then, if the operating conditions are such that the controller determines that the engine is producing a relatively low amount of NOx (e.g., low DEF dosing levels, low engine fueling, etc.), the controller examines the continuously sampled data in order to identify the minimum sensed value during low NOx production. Once the controller has determined the maximum and minimum values, the controller determines the difference between the maximum and minimum values against a diagnostic threshold in order to assess whether the system output NOx sensor is responding correctly. If the difference does not exceed the diagnostic threshold, the controller determines that the system output NOx sensor is “stuck” and not responding adequately to changes in the amount of NOx in the exhaust stream. In response to this determination, the controller then issues a fault alert, which can include setting a fault code, notifying a user, and shifting NOx monitoring responsibility to the engine output NOx sensor. The systems and methods of the present disclosure provide the following technical benefits: more robust diagnostic capability by correlating NOx output with ammonia slip, and reduced processing demands as the controller selectively proactively analyzes system output NOx sensor data only when certain operating conditions are met, which reduces the demand on computing resources. Furthermore, the systems and methods herein provide a technical advantage by isolating the failure of the system output NOx sensor as a stuck-in failure in order to expedite repair or other remedial measures. Furthermore, the systems and methods herein proactively respond to a stuck system output NOx sensor by notifying a user and shifting emissions monitoring responsibility to a secondary sensor in order to reduce potential consequences caused by a failed sensor.

[0034] Reference will now be made to Figure 1FIG. 1 shows an engine exhaust aftertreatment system with a controller, in accordance with example embodiments. An engine system 10 includes an internal combustion engine 20 and an exhaust aftertreatment system 22 in exhaust receiving communication with the engine 20. According to one embodiment, the engine system 10 is implemented within a vehicle. The vehicle can include an on-road vehicle or an off-road vehicle, including but not limited to an over-the-road truck, a medium duty truck (e.g., a pickup truck, etc.), a sedan, a coupe, a tank, an airplane, a boat, and any other type of vehicle. Based on these configurations, various additional types of components can also be included in the system, such as a transmission, one or more gearboxes, pumps, actuators, or any component driven by the engine.

[0035] The engine 20 can be an internal combustion engine (e.g., a gasoline engine, a natural gas engine, or a diesel engine), a hybrid engine system (e.g., a combination of an internal combustion engine and an electric motor), and / or any other suitable engine. In the example shown, the engine 20 is configured as a compression-ignition engine powered by diesel fuel. Within the internal combustion engine 20, air from the atmosphere is combined with fuel and combusted to drive the engine. Combustion of the fuel and air in the compression chambers of the engine 20 produces exhaust gas, which is operatively discharged to an exhaust manifold and the exhaust aftertreatment system 22.

[0036] In the depicted example, the exhaust aftertreatment system 22 includes a diesel particulate filter (DPF) 40, a diesel oxidation catalyst (DOC) 30, a selective catalytic reduction (SCR) system 52 with an SCR catalyst 50, and an ammonia oxidation (AMOx) catalyst 60. The SCR system 52 also includes a reductant delivery system with a diesel exhaust fluid (DEF) source 54 that supplies DEF to a DEF doser 56 via a DEF line 58.

[0037] In the exhaust flow direction, as indicated by directional arrow 29, exhaust gas flows from engine 20 into an inlet pipe 24 of exhaust aftertreatment system 22. The exhaust gas flows from inlet pipe 24 into DOC 30 and exits the DOC into a first section 28A of exhaust piping. The exhaust gas flows from first section 28A of exhaust piping into DPF 40 and exits the DPF into a second section 28B of exhaust piping. The exhaust gas flows from second section 28B of exhaust piping into SCR catalyst 50 and exits the SCR catalyst into a third section 28C of exhaust piping. As the exhaust gas flows through second section 28B of exhaust piping, DEF is periodically dosed into the exhaust gas by DEF doser 56. Thus, second section 28B of exhaust piping functions as a decomposition chamber or tube to facilitate decomposition of the DEF into ammonia. The exhaust gas flows from third section 28C of exhaust piping into AMOx catalyst 60 and exits the AMOx catalyst into outlet pipe 26 before the exhaust gas is discharged from exhaust aftertreatment system 22. Based on the foregoing, in the illustrated embodiment, DOC 30 is positioned upstream of DPF 40 and SCR catalyst 50, and SCR catalyst 50 is positioned downstream of DPF 40 and upstream of AMOx catalyst 60. However, other arrangements of the components of exhaust aftertreatment system 22 are possible in alternative embodiments

[0038] DOC 30 can have any of a variety of flow-through designs. Generally, DOC 30 is configured to oxidize at least some particulate matter in the exhaust gas (e.g., soluble organic fraction of soot particles) and reduce unburned hydrocarbons and CO in the exhaust gas to compounds that are less harmful to the environment. For example, DOC 30 can be configured to reduce the concentration of hydrocarbons and CO in the exhaust gas to meet required emission standards for those components in the exhaust gas. An indirect result of the oxidation capabilities of DOC 30 is the ability of the DOC to oxidize NO to NO2. In this manner, the level of NO2 exiting DOC 30 is equal to the NO2 in the exhaust gas generated by engine 20 plus the NO2 converted from NO by the DOC.

[0039] DPF 40 can be any of a variety of flow-through or wall-flow designs and is configured to reduce the concentration of particulate matter (e.g., soot particles and ash) in the exhaust gas to meet or substantially meet required emission standards. DPF 40 traps particulate matter and other components and can therefore need to be periodically regenerated to burn off the trapped components. In addition, DPF 40 can be configured to oxidize NO to form NO2 without reliance on DOC 30.

[0040] As described above, the SCR system 52 can include a reductant delivery system having a source 54 of reductant (e.g., DEF), a pump, and a delivery mechanism or doser 56. The source 54 of reductant can be a container or tank capable of holding reductant, such as ammonia (NH3), DEF (e.g., urea), or diesel. The source 54 of reductant is in reductant supplying communication with a pump configured to pump reductant from the source to the delivery mechanism 56 via a reductant delivery line 58. The delivery mechanism 56 is positioned upstream of the SCR catalyst 50. The delivery mechanism 56 is selectively controllable to inject reductant directly into the exhaust stream prior to entering the SCR catalyst 50. In some embodiments, the reductant can be ammonia or DEF that decomposes to produce ammonia. As briefly described above, ammonia reacts with NOx in the presence of the SCR catalyst 50 to reduce the NOx into less harmful emissions, such as N2and H2O. The NOx in the exhaust stream includes NO2and NO. Generally, both NO2and NO are reduced to N2and H2O by various chemical reactions driven by the catalytic elements of the SCR catalyst in the presence of NH3.

[0041] The SCR catalyst 50 can be any of a variety of catalysts known in the art. For example, in some implementations, the SCR catalyst 50 is a vanadium-based catalyst, while in other implementations, the SCR catalyst is a zeolite-based catalyst, such as a copper zeolite or iron zeolite catalyst.

[0042] The AMOx catalyst 60 can be any of a variety of flow-through catalysts configured to react with ammonia to primarily produce nitrogen. As described above, the AMOx catalyst 60 is configured to remove ammonia that has escaped or exited from the SCR catalyst 50 without reacting with NOx in the exhaust. In certain instances, the exhaust aftertreatment system 22 can operate with or without an AMOx catalyst. Further, although the AMOx catalyst 60 is shown as a separate unit from the SCR catalyst 50 in FIG. 1, in some implementations, the AMOx catalyst can be integrated with the SCR catalyst, e.g., the AMOx catalyst and the SCR catalyst can be located within the same housing. According to the present disclosure, the SCR catalyst and the AMOx catalyst are positioned in series, with the SCR catalyst preceding the AMOx catalyst. As described above, in various other embodiments, the AMOx catalyst is not included in the exhaust aftertreatment system 22. Figure 1

[0043] As described above, the exhaust aftertreatment system 22 can include a variety of other components, such as a diesel particulate filter (DPF) 62, a diesel oxidation catalyst (DOC) 64, and a diesel exhaust fluid (DEF) injector 66. The DPF 62 is configured to remove soot from the exhaust stream. The DOC 64 is configured to oxidize hydrocarbons and carbon monoxide in the exhaust stream. The DEF injector 66 is configured to inject DEF into the exhaust stream to reduce NOx in the exhaust stream. Figure 1 ​As shown, a variety of sensors 25 are included in the engine system. The sensors 25 are coupled to the controller 100, particularly communicatively coupled to the controller 100, such that the controller 100 can monitor and acquire data indicative of the operation of the system 10. The sensors 25 can include one or more NOx sensors (e.g., to monitor the amount of NOx in the exhaust gas exiting the engine 20 or the aftertreatment system 22), temperature sensors (e.g., to determine the temperature of the bed of the SCR catalyst 50), flow sensors (e.g., to determine the flow rate of the exhaust gas through the aftertreatment system 22), ammonia sensors (e.g., to sense the amount of ammonia in the exhaust stream after the SCR system 52), or any other type of sensor capable of providing information related to the operation of the engine 20 and the aftertreatment system 22. In particular, the system includes at least one NOx sensor positioned downstream of the engine 20 (which is shown in Figure 1 as NOx sensor 16 at the engine outlet) and at least one NOx sensor positioned downstream of the aftertreatment system 22 (which is shown in Figure 1 as NOx sensor 17 at the system outlet (or exhaust pipe)). In the exemplary embodiment, the amount and timing of DEF dosing from the reductant source 54 to the SCR system 52 is based on a closed loop feedback system including the NOx sensor 16 at the engine outlet and the NOx sensor 17 at the system outlet. In this embodiment, the controller 100 determines the efficiency of the SCR system 52 by comparing the amount of NOx present in the exhaust gas before the SCR system (i.e., at the NOx sensor 16 at the engine outlet) and the amount of NOx present in the exhaust gas after the SCR system (i.e., at the NOx sensor 17 at the system outlet). Based on the determined efficiency, the controller then adjusts the amount and timing of DEF dosing.

[0044] Because there are various sensed values indicative of the amount of NOx remaining in the exhaust gas after passing through the exhaust aftertreatment system (e.g., the bed temperature of the SCR catalyst 50, the injection rate of DEF, the flow rate of the exhaust gas, etc.), the controller 100 can predict or otherwise determine the relative amount of NOx expected to remain in the exhaust gas after passing through the exhaust aftertreatment system based on analysis of these values.

[0045] Although the exhaust aftertreatment system 22 shown includes one of a DOC 30, a DPF 40, an SCR catalyst 50, and an AMOx catalyst 60 positioned at particular locations relative to one another along the exhaust flow path, in other embodiments, the exhaust aftertreatment system can include more than one or any of a variety of catalysts positioned in any of a variety of positions relative to one another along the exhaust flow path as desired.

[0046] Figure 1Also shown is an operator input / output (I / O) device 120. The operator I / O device 120 is communicatively coupled to the controller 100, allowing information to be exchanged between the controller 100 and the I / O device 120, wherein information can be communicated with... Figure 1 The determination of one or more components or controller 100 (described below) is related to the engine system 10. Operator I / O device 120 enables the operator of the engine system 10 to communicate with controller 100 and... Figure 1 The controller 100 communicates with one or more components of the engine system 10. For example, the operator input / output device 120 may include, but is not limited to, an interactive display, a touchscreen device, one or more buttons and switches, a voice command receiver, etc. In various alternative embodiments, the controller 100 and components described herein may be implemented with respect to non-vehicle applications (e.g., generators). Therefore, the I / O device may be application-specific. For example, in these cases, the I / O device may include a laptop computer, tablet computer, desktop computer, telephone, watch, personal digital assistant, etc. Via the I / O device 120, the controller 100 may provide fault or service notifications based on the determined state of the NOx sensor 17 at the system output.

[0047] because Figure 1 The components are shown as implemented in system 10, and controller 100 can be configured as one or more electronic control units (ECUs). Controller 100 can be separate from or included in at least one of a transmission control unit, exhaust aftertreatment control unit, powertrain control module, engine control module, etc. Figure 2 The function and structure of the controller 100 are described in more detail.

[0048] Vehicle components can communicate with each other or with foreign components (e.g., remote operators) using any type and any number of wired or wireless connections. Communication between controller 100 and vehicle components can be via any number of wired or wireless connections (e.g., any standard under IEEE 802). For example, wired connections can include serial cables, fiber optic cables, CAT5 cables, or any other form of wired connection. Wireless connections can include the Internet, Wi-Fi, cellular, radio, Bluetooth, ZigBee, etc. In one embodiment, a controller local area network (CAN) bus provides the exchange of signals, information, and / or data. The CAN bus includes any number of wired and wireless connections that provide the exchange of signals, information, and / or data. The CAN bus can include a local area network (LAN) or a wide area network (WAN), or can be connected to an external computer (e.g., via the Internet provided by an Internet service provider).

[0049] Now refer to Figure 2 This illustrates an example embodiment. Figure 1 A schematic diagram of the controller 100 of system 10. (See diagram below.) Figure 2 As shown, the controller 100 includes a processing circuit 110 with a processor 112 and a memory 114, a low-mode circuit 160, a high-mode circuit 162, a sampling circuit 164, a threshold circuit 166, a stuck circuit 168, and a communication interface 116. The controller 100 is configured to monitor operating condition data of the system 10, particularly data regarding possible ammonia slip (e.g., conditions indicating ammonia slip exceeding a threshold), to determine when the system 10 is operating in a high-NOx mode or a low-NOx mode. Based on this determination, the controller then determines the difference between the minimum and maximum sensing values ​​of the NOx sensor 17 at the system output and compares this difference with a diagnostic threshold to determine whether the NOx sensor 17 at the system output is responding correctly or whether the NOx sensor 17 at the system output is stuck.

[0050] In one configuration, low-mode circuitry 160, high-mode circuitry 162, sampling circuitry 164, thresholding circuitry 166, and latching circuitry 168 are implemented as a machine or computer-readable medium carrying or having stored thereon machine-executable instructions or data structures executable by a processor (such as processor 112). As described herein and in other uses, the instructions facilitate the performance of certain operations to achieve the reception and transmission of data. For example, the instructions may provide commands to, for instance, acquire data. In this respect, the machine-readable medium may include programmable logic defining the frequency of data acquisition (or data transmission). The computer-readable medium may include code, which may be written in any programming language, including but not limited to Java and any conventional procedural programming language, such as the "C" programming language or similar programming languages. The computer-readable program code may be executed on one processor or multiple remote processors. In the latter case, the remote processors may be interconnected via any type of network (e.g., CAN bus, etc.).

[0051] In another configuration, the low mode circuit 160, the high mode circuit 162, the sampling circuit 164, the threshold circuit 166, and the stuck circuit 168 are implemented as hardware units, such as an electronic control unit. Thus, the low mode circuit 160, the high mode circuit 162, the sampling circuit 164, the threshold circuit 166, and the stuck circuit 168 can be implemented as one or more circuit components, including but not limited to processing circuitry, network interfaces, peripherals, input devices, output devices, sensors, etc. In some embodiments, the low mode circuit 160, the high mode circuit 162, the sampling circuit 164, the threshold circuit 166, and the stuck circuit 168 can take the form of one or more analog circuits, electronic circuits (e.g., integrated circuits (ICs), discrete circuits, system-on-chip (SOC) circuits, microcontrollers, etc.), telecommunication circuits, hybrid circuits, and any other type of “circuit.” In this regard, the low mode circuit 160, the high mode circuit 162, the sampling circuit 164, the threshold circuit 166, and the stuck circuit 168 can include any type of components for accomplishing or facilitating the implementation of the operations described herein. For example, the circuits described herein can include one or more transistors, logic gates (e.g., NAND, AND, NOR, OR, XOR, NOT, XNOR, etc.), resistors, multiplexers, registers, capacitors, inductors, diodes, wires, etc. The low mode circuit 160, the high mode circuit 162, the sampling circuit 164, the threshold circuit 166, and the stuck circuit 168 can also include programmable hardware devices, such as field programmable gate arrays, programmable array logic, programmable logic devices, etc. The low mode circuit 160, the high mode circuit 162, the sampling circuit 164, the threshold circuit 166, and the stuck circuit 168 can include one or more memory devices for storing instructions that can be executed by a processor(s) of the low mode circuit 160, the high mode circuit 162, the sampling circuit 164, the threshold circuit 166, and the stuck circuit 168. The one or more memory devices and the processor(s) can have the same definitions as provided herein with respect to the definitions of the memory 114 and the processor 112. In some hardware unit configurations, the low mode circuit 160, the high mode circuit 162, the sampling circuit 164, the threshold circuit 166, and the stuck circuit 168 can be geographically dispersed in various locations in the vehicle. Alternatively and as shown, the low mode circuit 160, the high mode circuit 162, the sampling circuit 164, the threshold circuit 166, and the stuck circuit 168 can be implemented in or within a single unit / housing, which is shown as the controller 100.

[0052] In the illustrated example, the controller 100 includes a processing circuit 110 having a processor 112 and a memory 114. The processing circuit 110 can be structured or configured to execute or implement the instructions, commands, and / or control processes described herein with respect to the low mode circuit 160, the high mode circuit 162, the sampling circuit 164, the threshold circuit 166, and the stuck circuit 168. The depicted configuration represents the low mode circuit 160, the high mode circuit 162, the sampling circuit 164, the threshold circuit 166, and the stuck circuit 168 as machine- or computer-readable instructions. However, as noted above, this illustration is not meant to be limiting, as the present disclosure contemplates other embodiments in which the low mode circuit 160, the high mode circuit 162, the sampling circuit 164, the threshold circuit 166, and the stuck circuit 168, or at least one of the low mode circuit 160, the high mode circuit 162, the sampling circuit 164, the threshold circuit 166, and the stuck circuit 168, are configured as hardware units. All such combinations and variations are considered to be within the scope of the present disclosure.

[0053] The processor 112 can be implemented as a single-chip or multi-chip processor designed for the particular function(s) described herein, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof. The processor can be a microprocessor or any conventional processor or state machine. The processor can also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some embodiments, one or more processors can be shared by multiple circuits (e.g., the low mode circuit 160, the high mode circuit 162, the sampling circuit 164, the threshold circuit 166, and the stuck circuit 168 can include or otherwise share the same processor, which in some example embodiments can execute instructions stored or otherwise accessed via different regions of memory). Alternatively or additionally, one or more processors can be structured to perform or otherwise execute certain operations independently of one or more co-processors. In other example embodiments, two or more processors can be coupled via a bus to enable independent, parallel, pipelined, or multithreaded instruction execution. All such variations are considered to be within the scope of the present disclosure.

[0054] The memory 114 (e.g., memory unit, storage device) can include one or more devices (e.g., RAM, ROM, flash memory, hard disk storage) for storing data and / or computer code for completing or facilitating the various processes, layers and modules described in the present disclosure. The memory 114 can be coupled to the processor 112, such that the processor 112 can

[0055] The low mode circuit 160 is configured or structured to analyze operating conditions with respect to the engine 20 and the aftertreatment system 22 and to predict or determine that the system 22 is outputting a relatively low amount of NOx (low NOx mode or operating mode). The relatively low amount of NOx can be defined as a predetermined threshold or low NOx mode operating condition. In some embodiments, the predetermined threshold is established based on a lookup table or map of NOx output stored in the memory 114. The operating condition data is received from the sensors 25 and includes at least one of the following: a fueling level of the engine 20, a temperature of the SCR catalyst 50 bed, an injection rate of DEF, an exhaust flow rate through the aftertreatment system 22, and an amount of NOx produced by the engine 20 (i.e., an amount of engine out NOx read by the NOx sensor 16 at the engine output). The low mode circuit 160 then analyzes the data in order to determine the amount of NOx output by the system. For example, if the fueling level of the engine 20 is low, indicating that the engine 20 is in a low fueling state (e.g., less than 5-20 mg / stroke), the low mode circuit 160 determines that the aftertreatment system 22 is outputting a low amount of NOx because an engine in a low fueling state produces less NOx. In another example, if the temperature of the SCR catalyst 50 bed is at or above a predetermined operating temperature (i.e., a temperature at which the SCR catalyst 50 is able to effectively react with NOx and ammonia in the exhaust stream), the low mode circuit 160 determines that the aftertreatment system 22 is outputting a low amount of NOx because the low mode circuit expects the SCR system 52 to be working effectively to reduce NOx in the exhaust stream. Further, if the operating condition data indicates that ammonia slip is not expected, or if the high mode circuit 162 does not determine a high ammonia slip (discussed in further depth below), the low mode circuit 160 determines that the system is outputting NOx as low.

[0056] Once the low mode circuit 160 determines that the system output NOx is low (i.e., at or below a predetermined threshold, thereby satisfying the low NOx mode operating condition), the low mode circuit 160 continues to monitor the operating condition data to determine whether the low system output NOx persists. If the determined low system output NOx condition persists for a predetermined period of time (e.g., if the engine 20 remains in the low fueling state for more than the predetermined period of time), the low mode circuit 160 sets a low system output NOx flag. The amount of the predetermined period of time can be set by a user via the operator I / O device 120 or can be automatically set by the low mode circuit 160 based on the operating condition data or other information (e.g., the age of components in the aftertreatment system). In an exemplary embodiment, the predetermined period of time is 5-100 seconds. Alternatively, if the determined low system output NOx condition fails to persist for the predetermined period of time, the low mode circuit 160 does not set the low system output NOx flag. Further, if the low mode circuit 160 initially sets the low system output NOx flag, but determines that the condition no longer persists, the low mode circuit 160 withdraws or resets the low system output NOx flag. Thus, the low system output NOx flag is an internal marker of the controller 100 that indicates that the low mode circuit 160 has determined or predicted a condition of low system output NOx and is used to trigger the sampling circuit 164 to take relevant data from the system output NOx sensor 17.

[0057] The high mode circuit 162 is configured or structured to analyze operating conditions regarding the engine 20 and the aftertreatment system 22 and determine that the system 22 is outputting a relatively high amount of NOx (high NOx mode or operating mode). The relatively high amount of NOx can be defined as a predetermined threshold or high NOx mode operating condition. In some embodiments, the predetermined threshold is established based on a lookup table or map of NOx output stored in the memory 114. The determination is made if the high mode circuit 162 determines that the operating conditions of the engine 20 and the aftertreatment system 22 indicate that the SCR system 52 has a low conversion efficiency or there is ammonia slip. The operating condition data is received from the sensors 25 and includes at least one of the following: the temperature of the SCR catalyst 50 bed, the injection rate of DEF, the exhaust flow rate through the aftertreatment system 22, and the amount of NOx produced by the engine 20 (i.e., the engine output NOx read by the engine output NOx sensor 16). The high mode circuit 162 then analyzes this data to determine whether there is a condition of low SCR efficiency or high ammonia slip.

[0058] In example embodiments, low SCR efficiency refers to a situation where conversion efficiency (i.e., the percentage of NOx in the exhaust gas entering the SCR system 52 that is reduced by the SCR catalyst 50) is less than a predefined threshold (e.g., 85%). Thus, if the operating condition data indicates that the SCR conversion efficiency is less than 85%, the high mode circuit 162 determines that the SCR system 52 is experiencing a low efficiency period. For example, the high mode circuit 162 determines that the SCR system 52 is experiencing a low efficiency period if the temperature of the SCR catalyst 50 bed is less than 220°C, if the temperature of the SCR catalyst 50 bed is greater than 450°C, if the exhaust gas flow rate is greater than 200-400 g / s, or if the engine out NOx flow rate is greater than 0.25-0.4 g / s. In some embodiments, the high mode circuit 162 determines that the SCR system 52 is experiencing low efficiency based on transient deNOx (i.e., NOx conversion). Transient deNOx is determined based on the deviation of the engine out NOx from a lagging moving average. If the transient deNOx is a relatively high positive deviation (e.g., 50-200 ppm), the transient deNOx is determined to be poor, which can indicate low SCR efficiency.

[0059] In example embodiments, high ammonia slip refers to situations in which the amount of ammonia remaining in the exhaust stream after passing through the SCR system 52 is between 25-500 ppm (or in another range, or above a predefined threshold). Thus, if the operating condition data indicates that there are conditions in which the amount of ammonia remaining in the exhaust stream is greater than 25 ppm, the high mode circuit 162 determines or predicts that the SCR system 52 is experiencing a period of high ammonia slip. For example, if the temperature of the SCR catalyst 50 bed exhibits a high rate of change, the high mode circuit 162 determines that there are conditions in which the SCR system 52 is experiencing a period of high ammonia slip. The rate of change is calibrated to vary with the temperature of the SCR catalyst 50 bed so as to match the catalyst storage characteristics to the catalyst temperature, but is generally adjusted to a range of 0.2-1 °C / s. A time constant filter (e.g., 10-300 seconds) is applied to the rate of change so as to model the dynamic ammonia release profile of the catalyst. At lower SCR catalyst 50 bed temperatures, ammonia release is triggered by a higher rate of temperature change because the ammonia storage capacity is greater at lower SCR catalyst bed temperatures. Thus, a high rate of temperature change can be found at low SCR catalyst 50 bed temperatures or high ammonia storage. Because a high rate of temperature change is correlated with high ammonia slip, high ammonia slip can also be found at low SCR catalyst 50 bed temperatures or high ammonia storage. Ammonia storage can be monitored by a timer that tracks the dosing of high ammonia to NOx ratios (ANR) for various time periods (e.g., 100-300 seconds) for SCR catalyst 50 bed temperatures between a particular temperature range (e.g., 200-300 °C). The timer is in place to ensure that there is excess ammonia available in storage and resets the timer when conditions indicate that storage is lost (e.g., SCR catalyst 50 bed temperature is above 400 °C, vehicle is keyed off for more than 24 hours, etc.). Ammonia storage can also be determined based on an ammonia release model that estimates the amount of ammonia released from ammonia storage as a function of operating condition data (e.g., SCR catalyst 50 bed temperature, exhaust stream, DEF dosing, etc.). The high mode circuit 162 can also determine that there are conditions of high ammonia slip based on data received from an ammonia sensor.

[0060] In other embodiments, the high mode circuit 162 can determine the amount of ammonia slip based on the operating condition data. In these embodiments, the high mode circuit determines or estimates the actual amount of ammonia slip, rather than determining or predicting that there are conditions of ammonia slip. The estimate can be based on an ammonia release model, data received from an ammonia sensor, or one or more algorithms, lookup tables, etc. that correlate certain data to an estimate of the amount of ammonia slip (e.g., SCR catalyst 50 bed temperature, DEF dosing level, etc.).

[0061] Accordingly, the high mode circuit 162 can determine that ammonia slip is occurring or likely to occur based on various operating data. Alternatively or additionally, the high mode circuit 162 can determine an actual, predicted, or estimated amount of ammonia slip. In either case, the presence of ammonia slip (and sometimes the amount of ammonia slip) can be determined and utilized by the controller.

[0062] In some embodiments, only one condition (i.e., low SCR efficiency or high ammonia slip) is used / satisfied for the high mode circuit to determine high system output NOx. In other embodiments, both conditions are utilized or satisfied for the high mode circuit to determine high system output NOx.

[0063] Once the high mode circuit 162 determines that the system output NOx is high (i.e., at or above a threshold, thereby satisfying the high NOx mode operating condition), the high mode circuit 162 continues to monitor the operating condition data to determine whether the high system output NOx persists. If the determined condition of high system output NOx persists for a predetermined period of time (e.g., if the temperature of the SCR catalyst 50 remains low for a predetermined period of time), the high mode circuit 162 sets a high system output NOx flag. The amount of the predetermined period of time can be set by a user via the operator I / O device or can be automatically set by the high mode circuit 162 based on the operating condition data or other information (e.g., the age of components in the aftertreatment system). In an exemplary embodiment, the predetermined period of time is equal to 30-300 seconds. Alternatively, if the determined condition of high system output NOx fails to persist for the predetermined period of time, the high mode circuit 162 does not set the high system output NOx flag. Furthermore, if the high mode circuit 162 initially sets the high system output NOx flag, but determines that the condition no longer persists, the high mode circuit 162 withdraws or resets the high system output NOx flag. Accordingly, the high system output NOx flag is an internal flag of the controller 100 that indicates that the high mode circuit 162 has determined or predicted the condition of high system output NOx and is used to trigger the sampling circuit 164 to take relevant data from the NOx sensor 17 at the system output.

[0064] In some embodiments, the low mode circuit 160 and the high mode circuit 162 operate in a feedback loop, with the results of such analysis by one circuit used as an input to the other circuit. For example, if the low mode circuit 160 sets the low system output NOx flag, the high mode circuit 162 automatically suspends analysis because the conditions of low system output NOx and high system output NOx cannot exist simultaneously. Alternatively, if the low mode circuit 160 does not determine low system output NOx, the high mode circuit 162 considers this information for its determination of high system output NOx.

[0065] The sampling circuit 164 is configured or structured to receive the low system output NOx flag from the low mode circuit 160 or the high system output NOx flag from the high mode circuit 162 and to extract data from the system output NOx sensor 17 accordingly. When the sampling circuit 164 receives the low system output NOx flag, the sampling circuit 164 identifies a minimum value of NOx values sensed by the system output NOx sensor 17 during the time that the low system output NOx flag (or indicator / indication) is set. Alternatively, when the sampling circuit 164 receives the high system output NOx flag, the sampling circuit 164 identifies a maximum value of NOx values sensed by the system output NOx sensor 17 during the time that the high system output NOx flag is set. In one embodiment, the sampling circuit 164 does not sample sensed data from the system output NOx sensor 17 unless the low system output NOx flag or the high system output NOx flag is set, in order to reduce the demand on the processing circuit 110, such that the low system output NOx flag and the high system output NOx flag are trigger conditions for the sampling circuit 164. Once the sampling circuit 164 has identified both the minimum value and the maximum value, the sampling circuit 164 determines a NOx delta value, which is defined as the difference between the minimum value and the maximum value. A higher NOx delta value indicates a relatively larger difference between the minimum value and the maximum value, which can indicate a healthy or error-free condition of the system output NOx sensor 17. A lower NOx delta value indicates a relatively smaller difference between the minimum value and the maximum value, which can indicate a system output NOx sensor error.

[0066] The threshold circuit 166 is configured or structured to receive the NOx delta from the sampling circuit 164 and compare the NOx delta to a diagnostic threshold. The diagnostic threshold indicates that the system output NOx sensor 17 is functioning properly (e.g., not "stuck"), and the diagnostic threshold can be based on the age of the system output NOx sensor 17, the status of other components within the system 10, or operator preference. In an exemplary embodiment, the diagnostic threshold is 2-20 ppm. If the NOx delta is less than the diagnostic threshold, which indicates that the system output NOx sensor 17 is not reacting sufficiently to the extreme of the system output NOx level, the threshold circuit 166 determines that the system output NOx sensor 17 is malfunctioning, particularly in a "stuck" fault condition. In response to this determination, the threshold circuit 166 sets the system output NOx sensor alarm. Thus, the system output NOx sensor alarm is an indication that the NOx sensor, particularly the system output NOx sensor, is stuck or malfunctioning. In some embodiments, the system output NOx sensor alarm includes a fault code, an indicator light, a notification broadcast to a remote service attendant, or an error message on a dashboard. Alternatively, if the NOx delta is equal to or greater than the diagnostic threshold, which would indicate that the system output NOx sensor 17 is operating as expected by reacting to the extreme of the system output NOx level, the threshold circuit 166 determines that the system output NOx sensor 17 is not malfunctioning or stuck. In response to this determination, the threshold circuit 166 refrains from setting or clearing the system output NOx sensor alarm.

[0067] Stuck circuit 168 is configured or structured to receive the system output NOx sensor alert from threshold circuit 166 and take appropriate action. In some embodiments, stuck circuit 168 notifies the user via operator I / O device 120 that the system output NOx sensor 17 has failed. In other embodiments, upon receiving an indication from threshold circuit 166 (e.g., setting a fault code), stuck circuit 168 exits the closed loop feedback control system for DEF dosing based on engine output NOx sensor 16 and system output NOx sensor 17 and begins DEF dosing in open loop control (i.e., one NOx sensor) based on engine output NOx sensor 16. In addition, stuck circuit 168 suspends monitoring of the SCR system 52 conversion efficiency, which is a metric used primarily to monitor NOx in the exhaust stream. Many jurisdictions have NOx regulations, some of which require tracking of exhaust pipe NOx output using system output NOx sensor 17. In this embodiment, stuck circuit 168 suspends this tracking in response to receiving an indication from threshold circuit 166. Thus, NOx monitoring is not transferred, but rather the entire SCR DEF control is transferred to engine output NOx sensor 16. In this regard, and as noted above, DEF dosing levels are determined by engine output NOx sensor 16 under open loop control. Feedback control will be exited as the system output NOx sensor is not trusted. In another embodiment, stuck circuit 168 disables monitoring of the SCR system 52 efficiency, thereby saving computational power.

[0068] According to Figure 3 A method 300 for diagnosing a NOx sensor is shown according to an example. Method 300 can be performed, at least in part, by controller 100 such that it can be referenced to help explain method 300.

[0069] Method 300 begins at process 302 and continues at decision 304 to determine whether a reset condition is met. If the reset condition is met (i.e., the inputs to method 300 are not trusted), the method returns to the beginning at step 302. For example, if system 10 includes a fault code for sensor 25, engine 20, or any other relevant component in system 10, the reset condition is met because method 300 cannot trust the inputs received from a faulty sensor or a faulty engine. If the reset condition is not met (i.e., there is no fault in system 10 that would cause uncertainty in the inputs to method 300), method 300 proceeds to steps 306 and 308.

[0070] At step 306, the controller 100 samples, and in particular continuously samples, the amount of NOx sensed by the NOx sensor 17 at the output of the system and tracks a minimum value. At step 308, the controller 100 samples, and in particular continuously samples, the amount of NOx sensed by the NOx sensor 17 at the output of the system and tracks a maximum value. Before the method 300 proceeds to step 310, and in this embodiment, certain prerequisites of steps 322 and 332 must be met. Thus, the method 300 continues at steps 318, 324 and 326.

[0071] At step 318, the controller 100 determines whether the system 10 is currently in a low NOx mode based on information from steps 312, 314, 316 and 330. At step 312, the controller receives information regarding the current operating conditions of the engine 20 and the aftertreatment system 22 and at step 314 analyzes the information to provide more advanced information regarding the operating conditions. For example, as discussed above with respect to the low mode circuit 160, the operating condition data can indicate that the temperature of the SCR catalyst 50 is at an operating temperature. At step 316, the controller 100 receives information regarding whether the engine 20 is in a low fueling mode. Based on the analysis of this information at step 318, if the controller 100 determines that the system 10 is not in a low NOx mode, the controller 100 proceeds to step 320. If the controller determines that the system 10 is operating in a low NOx mode, the controller 100 proceeds to step 322 and confirms that the low NOx mode persists by determining that the conditions of the low NOx mode persist for at least a predetermined period of time. If the conditions persist, the prerequisite of step 322 is met.

[0072] At step 324, the controller 100 determines, based on information from steps 312, 314, and 320, whether the current conditions indicate that the SCR system 52 has low conversion efficiency. For example, as discussed above with respect to the high mode circuit 162, information from steps 312 and 314 can indicate that instantaneous denitration is poor, which would indicate conditions of low SCR system 52 efficiency. At step 326, the controller 100 determines, based on information from steps 312, 314, and 320, whether the current conditions indicate that the SCR system 52 is experiencing high ammonia slip. This determination at step 326 can be a determination of the amount of ammonia slip or a determination that conditions of ammonia slip exist. For example, as discussed above with respect to the high mode circuit 162, information from steps 312 and 314 can indicate that the temperature change rate of the SCR catalyst 50 bed is high, which would indicate conditions of ammonia slip. Then, at step 328, if the result from either step 324 or step 326 is “yes” (i.e., the SCR system 52 has low conversion efficiency or high ammonia slip), the controller 100 determines that the system 10 is in a high NOx mode. If the system 10 is not in a high NOx mode, the method 300 proceeds to step 330. If the controller determines that the system 10 is operating in a high NOx mode, the controller 100 proceeds to step 332 and confirms that the high NOx mode persists by determining that the conditions in the high NOx mode persist for at least a predetermined period of time. If the conditions persist, the prerequisite condition of step 332 is met.

[0073] Once both steps 322 and 332 are met, the controller 100 proceeds to step 310 and determines the difference between the minimum of step 306 and the maximum of step 308. Then, at decision 334, this difference is compared to a diagnostic threshold. If the difference is greater than the diagnostic threshold (334: “yes”), the method 300 proceeds to step 336 and the controller rejects setting or clearing the system output NOx sensor alert. If the difference is less than the diagnostic threshold (334: “no”), the method proceeds to step 338 and the controller sets the system output NOx sensor alert. Then, the controller 100 provides a notification of the faulty system output NOx sensor 17 at step 340 and transfers responsibility for determining the amount and timing of DEF dosing to the engine output NOx sensor 16 at step 342.

[0074] As such, the system output NOx sensor alert is an indication that the NOx sensor, and in particular the system output NOx sensor, is “stuck” or malfunctioning. In some embodiments, the system output NOx sensor alert is or includes a fault code, an indicator light, a notification broadcast to a remote service attendant, or an error message on the instrument panel of the vehicle. Furthermore, the system output NOx sensor alert can trigger a related response, such as transferring responsibility for determining the amount and timing of DEF dosing to the engine output NOx sensor 16.

[0075] As used herein, the terms "approximately," "about," "substantially," and like terms are intended to have a broad meaning in harmony with the common and accepted usage of the same in the art to which the subject matter of this disclosure pertains. It should be understood by those skilled in the art who read the present disclosure that these terms are intended to allow for a certain level of variability as would be expected by one of ordinary skill in the art, and are not intended to be absolute or perfect precision. Thus, these terms should be interpreted as indicating near or approximately correct within a desired range of values and do not have to indicate exact or perfect comprehension or memory as of the specified value.

[0076] It should be noted that the terms "exemplary," and variations thereof, as used herein merely mean possible examples of implementations, and nothing less, and these terms are not meant to convey a limitation of the scope of the disclosure to the features or components of the examples described in connection therewith. Further, any element of an example disclosed herein can be combined with any element of any other example disclosed herein, or used in any other example.

[0077] The term "coupled" and variations thereof, as used herein, mean the joining of two members directly or indirectly to one another. Such joining can be stationary (e.g., permanent or fixed) or moveable (e.g., removable or releasable). Such joining can be achieved either directly, using only the components of the objects that are coupled to one another and any intervening components, or indirectly, using one or more separate intervening components. If "coupled" or variations thereof are modified by an additional term (e.g., directly coupled), the general definition of "coupled" provided above is modified by the plain language meaning of the additional term (e.g., "directly coupled means that two members are coupled and not any intervening components). Such coupling can be mechanical, electrical, or fluidic. For example, circuit A is communicatively "coupled" to circuit B can mean that circuit A is directly in communication with circuit B (i.e., no intermediaries) or indirectly in communication with circuit B (e.g., through one or more intermediaries).

[0078] References to element positions (e.g., "top," "bottom," "over," "under") herein are made for the purpose of describing the orientation of various elements in the figures. It should be noted that the orientation of the various elements can be different according to other example embodiments, and such variations are considered to be within the present disclosure.

[0079] Although the terms "first," "second," "third," etc. can be used herein to describe various elements or information, these elements or information should not be limited by these terms. These terms are only used to distinguish one element or information from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element without departing from the scope of the disclosure. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed terms. Figure 2Various circuits having specific functionality are shown in FIG. 1, but it should be understood that the controller 100 can include any number of circuits for accomplishing the functionality described herein. For example, the activities and functionality of the low mode circuit 160, the high mode circuit 162, the sampling circuit 164, the threshold circuit 166, and the stuck circuit 168 can be combined into multiple circuits or a single circuit. Additional circuits having additional functionality can also be included. Furthermore, the controller 100 can also control other activities beyond the scope of the present disclosure.

[0080] As described above, and in one configuration, "circuitry" can be implemented in Figure 2 a machine-readable medium for execution by various types of processors. The recognition circuitry can include, for example, one or more physical or logical blocks of computer instructions. However, the executable file of the recognition circuitry need not be physically located together, but can comprise different instructions stored in different locations which, when joined logically together, include and implement the circuitry and accomplish the stated purpose(s) of the circuitry. Indeed, the circuitry of the computer-readable program code can be a single instruction, or many instructions, and can even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data can be identified and illustrated herein within the circuitry, and can be embodied in any suitable form and organized within any suitable type of data structure. The operational data can be collected as a single data set, or can be distributed over different locations including over different storage devices, and can exist, at least partially, merely as electronic signals on a system or network.

[0081] Although the term "processor" is used herein, the term "processor" and "processing circuitry" are meant to be broadly interpreted. In this regard, the "processor" can be implemented as one or more Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), Digital Signal Processors (DSPs), or other suitable electronic data processing components that are constructed to perform the instructions provided by memory. The one or more processors can take the form of a single core processor, multi-core processor (e.g., dual-core processor, tri-core processor, quad-core processor, etc.), microprocessor, etc. In some embodiments, the one or more processors can be external to the apparatus, e.g., the one or more processors can be a remote processor (e.g., a cloud-based processor). Alternatively or additionally, the one or more processors can be internal and / or local to the apparatus. In this regard, a given circuit or component thereof can be locally disposed (e.g., as part of a local server, local computing system, etc.) or remotely disposed (e.g., as part of a remote server such as a cloud-based server). To this end, "circuitry" described herein can include components distributed across one or more locations.

[0082] Embodiments within the scope of the present disclosure include program products comprising machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine-readable media can be any available media that can be accessed by a computer or other machine with a processor. By way of example, such machine-readable media can include RAM, ROM, EPROM, EEPROM, or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code in the form of machine-executable instructions or data structures and which can be accessed by a general purpose or special purpose computer or other machine with a processor. Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions include, for example, instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing machines to perform a certain function or group of functions.

[0083] Although the flow diagrams and associated descriptions can show a specific order of method steps, the order of these steps can differ from what is depicted and described, unless specified differently above. Also, two or more steps can be performed concurrently or with partial concurrence. Such variation can depend, for example, on the software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure. Likewise, software implementations could be accomplished with standard programming techniques with rule-based logic and other logic to accomplish various connection steps, processing steps, comparison steps, and decision steps.

Claims

1. A system for diagnosing a NOx sensor, comprising: a controller including at least one processor coupled to a memory storing instructions that, when executed by the at least one processor, cause the controller to perform operations including: receiving data indicative of an operating condition of at least one of an engine or an aftertreatment system; determining, based on an analysis of the data indicative of the operating condition, that an amount of NOx output from the aftertreatment system during a first time period satisfies a low NOx operating mode condition; determining, based on data regarding operation of the aftertreatment system, that there is an operating condition regarding ammonia slip during a second time period; in response to determining that there is the operating condition regarding ammonia slip, determining that the amount of NOx output from the aftertreatment system satisfies a high NOx operating mode condition; taking a minimum of the amount of NOx output from the aftertreatment system during the first time period; taking a maximum of the amount of NOx output from the aftertreatment system during the second time period; comparing a difference between the minimum and the maximum to a diagnostic threshold; and in response to the difference being less than the diagnostic threshold, setting an alert. The data regarding operation of the aftertreatment system includes a temperature change rate of a SCR catalyst in the aftertreatment system or an amount of ammonia storage in the aftertreatment system.

2. The system of claim 1, wherein, Determining that the amount of NOx output from the aftertreatment system satisfies the low NOx operating mode condition includes at least one of determining that a fueling level of the engine is below a fueling threshold, determining that a temperature of a selective catalytic reduction (SCR) catalyst in the aftertreatment system is at or above a temperature threshold, or determining that an amount of ammonia slip is below an ammonia threshold.

3. The system of claim 1 or 2, wherein, In response to the first time period exceeding a time threshold, taking the minimum during the first time period.

4. The system of claim 1 or 2, wherein, Determining that there is the operating condition regarding ammonia slip includes at least one of determining an amount of ammonia slip or determining that a conversion efficiency of a selective catalytic reduction (SCR) catalyst in the aftertreatment system is below an efficiency threshold.

5. The system of claim 1 or 2, wherein, In response to the second time period exceeding a time threshold, taking the maximum during the second time period.

6. The system of claim 1 or 2, wherein, 7. The system of claim 1 or 2, further in response to the difference being less than the diagnostic threshold, changing a closed loop feedback loop utilizing both an exhaust gas sensor at a system output end and an exhaust gas sensor at an engine output end to an open loop feedback loop utilizing the exhaust gas sensor at the engine output end.

8. A method for diagnosing a NOx sensor, the method comprising: receiving data indicative of an operating condition of at least one of an engine or an aftertreatment system; determining, based on the data indicative of an operating condition, that an amount of NOx output from the aftertreatment system during a first time period satisfies a low NOx operating mode condition; determining, based on data regarding operation of the aftertreatment system, that there is an operating condition regarding ammonia slip during a second time period; ​ in response to determining that the operating condition exists with respect to ammonia slip, determining that the amount of NOx output from the aftertreatment system satisfies a high NOx operating mode condition; taking a minimum value of the amount of NOx output from the aftertreatment system during the first time period; taking a maximum value of the amount of NOx output from the aftertreatment system during the second time period; comparing a difference between the minimum value and the maximum value to a diagnostic threshold value; and in response to the difference being less than the diagnostic threshold value, setting an alert with respect to the NOx sensor.

9. The method of claim 8, wherein, The data with respect to operation of the aftertreatment system includes a temperature change rate of a SCR catalyst in the aftertreatment system or an amount of ammonia storage in the aftertreatment system.

10. The method of claim 8 or 9, wherein, Determining that the amount of NOx output from the aftertreatment system satisfies the low NOx operating mode condition includes at least one of determining that a fueling level of the engine is below a fueling threshold value, determining that a temperature of a selective catalytic reduction (SCR) catalyst in the aftertreatment system is at or above a temperature threshold value, or determining that an amount of ammonia slip is below an ammonia threshold value.

11. The method of claim 8 or 9, wherein, In response to the first time period exceeding a time threshold value, taking the minimum value during the first time period.

12. The method of claim 8 or 9, wherein, Determining that the operating condition exists with respect to ammonia slip includes at least one of determining an amount of ammonia slip or determining that a conversion efficiency of a selective catalytic reduction (SCR) catalyst in the aftertreatment system is below an efficiency threshold value.

13. The method of claim 8 or 9, wherein, In response to the second time period exceeding a time threshold value, taking the maximum value during the second time period.

14. The method of claim 8 or 9, further in response to the difference being less than the diagnostic threshold value, changing a closed loop feedback loop utilizing both an engine-out exhaust sensor and an engine-out exhaust sensor from the system output to an open loop feedback loop utilizing the engine-out exhaust sensor.

15. A system for diagnosing a NOx sensor, comprising: an aftertreatment system in exhaust receiving communication with an engine; and a controller coupled to the aftertreatment system and the engine, the controller configured to: receive data indicative of an operating condition of at least one of the engine or the aftertreatment system; based on the data indicative of the operating condition, determine that an amount of NOx output from the aftertreatment system during a first time period satisfies a low NOx operating mode condition; based on data with respect to operation of the aftertreatment system, determine that an operating condition exists with respect to ammonia slip during a second time period; in response to determining that the operating condition exists with respect to ammonia slip, determine that the amount of NOx output from the aftertreatment system satisfies a high NOx operating mode condition; take a minimum value of the amount of NOx output from the aftertreatment system during the first time period; take a maximum value of the amount of NOx output from the aftertreatment system during the second time period; compare a difference between the minimum value and the maximum value to a diagnostic threshold value; and in response to the difference being less than the diagnostic threshold value, set an alert.

16. The system of claim 15, wherein, Determining that the amount of NOx output from the aftertreatment system satisfies the low NOx operating mode condition includes at least one of determining that a fueling level of the engine is below a fueling threshold, determining that a temperature of a selective catalytic reduction (SCR) catalyst in the aftertreatment system is at or above a temperature threshold, or determining that an amount of ammonia slip is below an ammonia threshold.

17. The system of claim 15 or 16, wherein, Taking the minimum value during the first time period in response to the first time period exceeding a time threshold.

18. The system of claim 15 or 16, wherein, Determining that the operating condition with respect to ammonia slip exists includes at least one of determining an amount of ammonia slip or determining that a conversion efficiency of a selective catalytic reduction (SCR) catalyst in the aftertreatment system is below an efficiency threshold.

19. The system of claim 15 or 16, wherein, Taking the maximum value during the second time period in response to the second time period exceeding a time threshold.

20. The system of claim 15 or 16, further responsive to the difference being less than the diagnostic threshold, changing a closed loop feedback loop utilizing both an exhaust gas sensor at a system output and an exhaust gas sensor at an engine output to an open loop feedback loop utilizing the exhaust gas sensor at the engine output.

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