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Diagnostic processes for determining whether a NO x sensor is in a stuck-in-range failure mode may be performed when the NO x sensor reaches an operational temperature and before the oxygen pumps of the NO x sensor are activated and/or during operation. The processes may include interpreting values of a parameter indicative an amount of O 2 and/or NO x measured by the NO x sensor. The processes include determining if the values of the parameter exceed a threshold value and indicating a failure of the NO x sensor responsive to the values not exceeding the threshold value. In some implementations, the processes may include increasing an amount of O 2 in a chamber of the NO x sensor. Increasing the amount of O 2 in the chamber of the NO x sensor may include deactivating an oxygen pump of the NO x sensor or reducing an amount of O 2 removed via an oxygen pump of the NO x sensor.
1. A system comprising:
a NO x sensor comprising an oxygen pump; and
a controller configured to:
at a time at which the oxygen pump of the NO x sensor has not been activated, interpret one or more values of a parameter indicative an amount of O 2 and/or NO x measured by the NO x sensor responsive to the NO x sensor reaching an operational temperature;
determine if the one or more values of the parameter exceed a threshold value; and
indicate a failure of the NO x sensor responsive to the one or more values of the parameter not exceeding the threshold value.
2. The system of claim 1 , wherein the indicating of the failure of the NO x sensor comprises setting a value for a parameter to a value indicating that the NO x sensor is in the stuck-in-range failure mode.
3. The system of claim 1 , wherein the indicating of the failure of the NO x sensor comprises lighting a malfunction indicator lamp.
4. The system of claim 1 , wherein the one or more values of the parameter indicative the amount of O 2 and/or NO x measured by the NO x sensor are based on a measured pumping current.
5. The system of claim 1 , wherein the threshold value is a value indicative of an amount of O 2 and/or NO x of 100 ppm.
6. The system of claim 1 , wherein the threshold value is a value indicative of an amount of O 2 and/or NO x of 500 ppm.
7. The system of claim 1 , wherein the threshold value is a value indicative of an amount of O 2 and/or NO x of less than 1000 ppm.
8. A system comprising:
a NO x sensor; and
a controller configured to:
at a time at which(i) an oxygen pump of the NO x sensor has not been activated, or (ii) an amount of O 2 in a chamber of the NO x sensor has not been increased, interpret one or more values of a parameter indicative an amount of O 2 and/or NO x measured by the NO x sensor responsive to the NO x sensor reaching an operational temperature;
calculate a variation of the one or more values of the parameter indicative of the amount of O 2 and/or NO x measured by the NO x sensor;
determine if the calculated variation exceeds a threshold value; and
indicate a failure of the NO x sensor responsive to the calculated variation not exceeding the threshold value;
wherein the threshold value is a value indicative of an amount of O 2 and/or NO x of less than 1000 ppm.
9. The system of claim 8 , wherein the controller is further configured to:
store the calculated variation;
calculate an average of a plurality of stored calculated variations;
wherein determining if the calculated variation exceeds the threshold value comprises determining if the average of the plurality of stored calculated variations exceeds the threshold value; and
wherein indicating the failure of the NO x sensor is responsive to the average of the plurality of stored calculated variations not exceeding the threshold value.
10. The system of claim 8 , wherein the indicating of the failure of the NO x sensor comprises setting a value for a parameter to a value indicating that the NO x sensor is in the stuck-in-range failure mode or lighting a malfunction indicator lamp.