Methods and systems for a particulate matter sensor

A method, comprising:

• during a drive cycle of an engine that begins with an engine start and ends with an engine shut down:
• during a warm-up mode, increasing a sensor temperature to a first temperature greater than an exhaust gas temperature but lower than a temperature at which soot burns to repel particulate matter from a sensing element, maintaining the sensor temperature at the first temperature, and not adjusting engine operating parameters based on a particulate matter sensor until the sensor reaches light-off temperature, the warm-up mode occurring responsive to the engine start;
• during a measurement mode, generating a particulate flow rate through a particulate filter based on particulate accumulation on the sensing element of the particulate matter sensor, and adjusting one or more engine operating parameters based on the sensor, at least one instance of the measurement mode occurring responsive to light-off of the particulate matter sensor after the engine start;
• and
• during a reduced contamination mode, increasing the sensor temperature to a second temperature greater than the exhaust gas temperature but lower than the temperature at which soot burns to repel particulate matter from the sensing element, maintaining the sensor temperature at the second temperature, and not adjusting the engine operating parameters based on the sensor, the reduced contamination mode occurring responsive to completion of the measurement mode.

A system, comprising:

• an engine with an exhaust system;
• a particulate matter sensor disposed downstream of a particulate filter in the exhaust system, the particulate matter sensor including a heater and a sensing element exposed to an exhaust gas stream;
• and
• an electronic control system in communication with the particulate matter sensor, the electronic control system including a storage medium storing non-transitory instructions to, during a measurement mode of a diagnostic test, generate a particulate flow rate through the particulate filter based on the particulate matter sensor, and adjust one or more engine operating parameters based on the particulate flow rate;
• and, during a reduced contamination mode of the diagnostic test, initiate operation of the heater to increase a sensor temperature to a first temperature greater than an exhaust gas temperature but lower than a temperature at which soot burns to repel particulate matter from the sensing element, maintain the sensor temperature at the first temperature until an engine shut-down event, and not adjust the engine operating parameters based on the sensor, the reduced contamination mode of the diagnostic test occurring after the measurement mode of the diagnostic test.

A method for a particulate matter sensor, comprising:

• generating an indication of particulate flow rate through a particulate filter based on particulate accumulation on a sensing element of the sensor, and diagnosing the particulate filter based on the flow rate;
• and
• responsive to determining that the diagnosing of the particulate filter is completed, heating the sensing element of the sensor to a temperature greater than an exhaust gas temperature but lower than a temperature at which soot burns to repel particulate from the sensing element;
• wherein heating the sensing element includes heating the sensor to the temperature greater than the exhaust gas temperature, and maintaining it greater than the exhaust gas temperature even as the exhaust gas temperature fluctuates with engine operating conditions, but less than the temperature at which soot burns, and not diagnosing the particulate filter.