Theory of Operation

WARNING: This page is about a different car, the 2011 RAM Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

The engine aftertreatment system monitors the soot load in the DOC/DPF Catalyst. Under normal operating conditions the aftertreatment Diesel Particulate Filter is self-cleaning, where soot is converted to ash. The soot load in the aftertreatment DOC/DPF Catalyst is estimated using the Exhaust Pressure Sensor and the calculated soot output of the engine. The Powertrain Control Module (PCM) will set this fault if it detects that the aftertreatment DOC/DPF Catalyst is plugged or that the differential pressure across the DOC/DPF Catalyst is above the calibrated moderately severe threshold limit. The PCM will illuminate the MIL lamp immediately when the diagnostic runs and fails. The driver will be notified via the vehicle's EVIC Message Center. The PCM will turn off the MIL lamp immediately after the soot load has dropped below the Moderately Severe Level Threshold.