Methods and systems are provided for on-board diagnostics of components of an exhaust gas heat recovery (EGHR) system including engine coolant temperature sensors coupled to the system. Degradation of one or more of a first coolant temperature sensor coupled upstream of a heat exchanger of the EGHR system and a second coolant temperature sensor coupled downstream of the heat exchanger may be indicated based on a difference between a modeled coolant temperature and a measured coolant temperature, the modeled coolant temperature based on one or more of heat transfer between a heater core and vehicle cabin, and heat transfer between exhaust flowing via the heat exchanger and coolant flowing through the heat exchanger.

A method, system, and apparatus are provided for improving accuracy of sensor readings reflecting measurements of at least one constituent in an engine exhaust. The sensor measurement is corrected or compensated for by applying to a gain correction factor to the reported sensor measurement. The gain correction factor is developed by determination of prior test sensor readings correlated with discrete sensor age levels, and with constituent concentrations to which those test sensors are exposed. By applying the determined gain correction factor to change the sensor's reported measurements, bias may be reduced and a more accurate measure of actual constituent levels is provided.

A power system for a work vehicle includes an engine that generates exhaust gas, an exhaust treatment system that treats the exhaust gas, and an electronic control system coupled to the engine and the exhaust treatment system and implementing a maintenance management system. The maintenance management system is configured to receive a first identifier associated with a first sensor or actuator device installed in the exhaust treatment system, store the first identifier in memory, receive a second identifier associated with a second sensor or actuator device installed in the power system of the work vehicle, compare the first identifier to the second identifier to determine that the first identifier differs from the second identifier and that the second sensor or actuator device is a replacement for the first sensor or actuator device in the exhaust treatment system, and clear any fault codes associated with the first sensor or actuator device.

A gas sensor includes a sensor element made of an oxygen-ion conductive solid electrolyte, at least one electrode provided to the sensor element so as to contact a measurement gas, and a controller configured to control the gas sensor. The sensor element is heated, by a heater provided to the sensor element, at a temperature higher than an operating temperature set in advance for a predetermined time period at start of the gas sensor, and then the temperature of the sensor element is decreased to the operating temperature.

An exhaust purification system comprises an exhaust purification catalyst 20, an NO.sub.X sensor 46, air-fuel ratio sensor 41 downstream of the catalyst 20, and a control and diagnosis device. The device alternately sets a target air-fuel ratio to a rich air-fuel ratio and a lean air-fuel ratio and switches the target air-fuel ratio from the rich air-fuel ratio to the lean air-fuel ratio when the output air-fuel ratio of the air-fuel ratio sensor becomes a rich judged air-fuel ratio or less. The device diagnoses abnormality of the catalyst based on the output of the NO.sub.X sensor. It diagnoses abnormality of the catalyst when the air-fuel ratio of the exhaust gas flowing into the catalyst is a rich air-fuel ratio, but does not diagnose abnormality of the catalyst when the air-fuel ratio of the exhaust gas flowing into the catalyst is a lean air-fuel ratio.

Systems and methods for diagnosing operation of a sensor of an exhaust system are presented. In one example, the systems and methods may diagnose operation of the sensor when an engine is combusting air and fuel. Further, operation of the sensor may be diagnosed when the engine is not combusting air and fuel so that vehicle occupants may not be disturbed by the diagnostic.

An exhaust system for a vehicle and method of operating the exhaust system. The exhaust system comprises an internal combustion engine, an exhaust throttle valve, and a pressure sensor. The method comprises the steps of: outputting an exhaust gas from the internal combustion engine; determining a flow factor for the exhaust throttle valve; conducting a diagnostic pressure analysis using one or more pressure readings from the pressure sensor; estimating a stuck position for the exhaust throttle valve; determining a flow limit based on the estimated stuck position; and mitigating one or more exhaust system effects based on the flow limit and/or the estimated stuck position.

An emissions test system includes a dilution tunnel, a clean circuit, a dirty circuit, and a sampling control module. The dilution tunnel is configured to receive exhaust gas from an engine and dilution gas from a dilution gas source. The clean circuit is configured to receive gas from the dilution tunnel. The dirty circuit is configured to receive gas from the dilution tunnel independent of the clean circuit. The sampling control module is configured to direct gas from the dilution tunnel to the dirty circuit when the engine is off at the start of a first test phase. The sampling control module is configured to direct gas from the dilution tunnel to the clean circuit at the end of the first test phase when the engine is switched on during the first test phase.

An engine diagnostic tool includes a diagnostic engine calibration module structured to include a plurality of diagnostic processes for operating an internal combustion engine system of an immobilized vehicle. One or more of the plurality of diagnostic processes are structured to be an intrusive diagnostic process for the internal combustion engine system, wherein the intrusive diagnostic process causes the internal combustion engine system to operate outside of one or more calibration parameters. The diagnostic engine module is further structured to control the order and timing of each diagnostic process in the plurality of diagnostic processes.

An exhaust gas sensor includes an element cover, a heater, a heater control section, and a cover state diagnosing section. The element cover accommodates a sensor element including a detection section and includes one or more gas flow holes. The heater heats the sensor element. The heater control section controls how the heater heats the sensor element. The cover state diagnosing section diagnoses a state of the element cover using heater information obtained when the heater is operated by the heater control section. The cover state diagnosing section includes a diagnosability determining section, which determines whether the state of the element cover is diagnosable based on an accuracy of the heater information obtained from an operating state of the heater and a surrounding environmental state of the element cover.