Systems and methods for running a NOx self-diagnostic test
AssigneeFord Global Technologies, LLC
InventorsIn Kwang Yoo, Michiel J. Van Nieuwstadt, Garth Michael Meyer
Life of this patent
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Abstract
Methods and systems are provided for detecting NOx sensor degradation based on results from a NOx sensor self-diagnostic (SD) test. In one example, a method may comprise: determining that a nitrogen oxide (NOx) sensor is degraded if outputs received from the sensor via a CAN bus during a self-diagnostic test are outside a threshold range. Additionally, only outputs received from the sensor during a self-diagnostic (SD) test performed after a first completed SD test after a key-off event, where the outputs are generated under conditions where a temperature at the sensor is less than a threshold, and an oxygen concentration is within a threshold range may be used to determine if the sensor is degraded.
Claims20
A method comprising:
- with an electronic controller communicating with a nitrogen oxide (NOx) sensor, determining that the NOx sensor measuring engine exhaust gas is degraded based on outputs received from the sensor during a self-diagnostic (SD) test performed after a first completed SD test after an ignition off event, only when the outputs are generated under conditions where the controller determines that a temperature at the sensor is less than a threshold, and an oxygen concentration is within a threshold range;
- and
- generating a warning via a vehicle display responsive to the determination that the sensor is degraded.
A method comprising:
- excluding a first completed self-diagnostic (SD) test result of a NOx sensor measuring exhaust gas after an engine ignition off event;
- excluding second and subsequent test results from a completed SD test if one or more of an exhaust gas temperature is greater than a threshold, and an oxygen concentration of the exhaust gas is outside a threshold range;
- otherwise not excluding second and subsequent test results from a completed SD test;
- determining that the sensor is degraded only when the non-excluded test results are different from a reference value by more than a threshold;
- and
- generating a warning via a display responsive to determining that the sensor is degraded.
A system comprising:
- a first NOx sensor positioned in an engine exhaust system upstream of a selective catalytic reduction (SCR) catalyst;
- a second NOx sensor positioned downstream of the SCR;
- a first temperature sensor aligned with the first NOx sensor relative to an exhaust gas flow in the exhaust system for measuring a temperature of exhaust gasses flowing past the first NOx sensor;
- a second temperature sensor aligned with the second NOx sensor relative to the exhaust gas flow in the exhaust system for measuring a temperature of exhaust gasses flowing past the second NOx sensor;
- and
- a controller in electrical communication with the first and second NOx sensors via a CAN bus, the controller having computer-readable instructions for:
- determining that one or more of the first NOx sensor and second NOx sensor is degraded based on outputs from the first NOx and temperature sensors, and the second NOx and temperature sensors, respectively, where the outputs are generated during a self-diagnostic test after a vehicle ignition key-off, and generating a warning via a vehicle display responsive to the determination that the sensor is degraded.
Dependencies are inferred from the claim text.