A Particulate Matter sensor should be replaced if a check engine light indicates a fault, when the Diesel Particulate Filter (DPF) itself is replaced, or when signs of failure appear. Common signs of failure include frequent or unnecessary DPF regeneration, reduced fuel efficiency, or diagnostic trouble codes related to emissions performance.

Prior to the invention of Particulate Matter sensors, Diesel Particulate Filter (DPF) monitoring was done indirectly – utilizing ΔP (differential pressure) sensors. Bosch began developing direct diesel Particulate Matter sensors in the mid-to-late 2000’s, with official rollout beginning as far back as 2013. This timing was closely tied to the announcement of Euro 6, and EPA 13/17 emission requirements that mandated on-board monitoring of DPF via real-time soot detection. Particulate Matter sensors offer far more accurate soot measurements compared to a ΔP sensor, while also having many additional benefits over a ΔP sensor.

The functional principle behind the Particulate Matter sensor is based on resistance measurement. Soot particles are deposited on an electrode structure and form conductive soot trails between the electrodes. Prior to each measurement phase, the sensor element is regenerated through heating so that the sensor element adopts a defined status before the start of the measurement process. The DPF diagnostic software then evaluates the functional capability of the DPF using the measured current.