Theory of Operation

The Diesel particulate filter is an inline canister filter located in the exhaust system between the engine and the muffler. This filter captures and stores ash particles created by the diesel combustion process. This filter is monitored by the ECM with a Differential Pressure Sensor. This sensor measures the difference in exhaust system pressure before and after the particulate filter through tube connections directly to the exhaust pipe. As ash accumulates in the filter, the exhaust pressure at the inlet side of the filter increases as compared to the pressure at the outlet side of the filter. The ECM monitors the sensor to determine when to perform a particulate filter regeneration procedure which is designed to clear "burn-off" the ash collected in the filter.

• When Monitored: 

  With the engine running.

• Set Condition: 

  The ECM detects incorrect exhaust flow through the particulate filter during certain engine operating conditions.

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. See  DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure