Method of verifying particulate matter sensor validity
A method for verifying the validity of an output of a particulate matter sensor mounted in an engine exhaust system downstream of a diesel particulate filter, the particulate matter sensor including a pair of electrodes spaced apart from each other, includes initiating regeneration of the diesel particulate filter, applying and maintaining a higher than nominal voltage across the electrodes following the step of initiating regeneration of the diesel particulate filter, and measuring an electrical parameter across the electrodes while the higher voltage is applied across the electrodes, where the electrical parameter is indicative of an amount of soot accumulated on the sensor. The reading of accumulated soot is evaluated to determine whether the sensor is indicating that the amount of accumulated soot is within an expected range based on a clean diesel particulate filter and the elevated applied voltage.
1. A method for verifying the validity of an output of a particulate matter sensor mounted in an engine exhaust system downstream of a diesel particulate filter, the particulate matter sensor comprising a pair of electrodes spaced apart from each other, the method comprising the steps of:
initiating regeneration of the diesel particulate filter;
applying and maintaining a first voltage across the electrodes following the step of initiating regeneration of the diesel particulate filter;
measuring an electrical parameter across the electrodes while the first voltage is applied across the electrodes, the electrical parameter being indicative of an amount of soot accumulated on the sensor;
evaluating the electrical parameter to determine whether the sensor is indicating that the amount of accumulated soot is within a first predetermined range;
determining that the sensor is operating properly if the electrical parameter is indicating that the amount of accumulated soot is within the first predetermined range.
2. The method of claim 1 further including the step of indicating that the sensor is not operating properly if the electrical parameter is not within the first predetermined range within a predetermined time interval after the first voltage is first applied across the electrodes.
3. The method of claim 1 further including the step of reducing the voltage applied across the electrodes from the first voltage to a second voltage, the second voltage being of lower magnitude than the first voltage.
4. The method of claim 3 wherein the voltage is reduced from the first level to the second level after the step of determining that the sensor is operating properly.
5. The method of claim 1 wherein, if the electrical parameter is indicating that the amount of accumulated soot is within the first predetermined range the method further includes the steps of:
commanding a sensor cleaning event;
measuring the electrical parameter after commanding the sensor cleaning event;
evaluating the electrical parameter to determine whether the sensor is indicating that the accumulated soot is being successfully cleaned from the sensor; and
indicating that the sensor is not operating properly if the sensor is not indicating that the accumulated soot is being successfully cleaned from the sensor.
6. The method of claim 1 further comprising controlling the engine so as to increase an amount of soot generated by the engine while the first voltage is applied and maintained across the electrodes.
7. The method of claim 6 wherein the step of controlling the engine comprises controlling exhaust gas recirculation to the engine.
8. The method of claim 6 wherein the step of controlling the engine comprises controlling engine fuel rail pressure.
9. An apparatus comprising:
a processor, and
a memory storing instructions that, when executed, cause the apparatus to:
initiate regeneration of the diesel particulate filter;
apply and maintain a first voltage across the electrodes following the step of initiating regeneration of the diesel particulate filter;
measure an electrical parameter across the electrodes while the first voltage is applied across the electrodes, the electrical parameter being indicative of an amount of soot accumulated on the sensor;
evaluate the electrical parameter to determine whether the sensor is indicating that the amount of accumulated soot is within a first predetermined range; and
determine that the sensor is operating properly if the electrical parameter is indicating that the amount of accumulated soot is within the first predetermined range.