For a complete wiring diagram Refer to Section 8WThe 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 and soot accumulate 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. When Monitored:With the engine running.Set Condition:The ECM detects differential pressure that are lower than expected for certain engine operating conditions for 2.0 seconds.Possible CausesDAMAGED EXHAUST SYSTEMLEAKING EXHAUST SYSTEMHIGH RESISTANCE IN EXHAUST DIFFERENTIAL PRESSURE SENSOR CIRCUITSHOSE/TUBE CONNECTIONS TO THE EXHAUST DIFFERENTIAL PRESSURE SENSOREXHAUST DIFFERENTIAL PRESSURE SENSORDIESEL PARTICULATE FILTERAlways perform the Pre-Diagnostic Troubleshooting procedure before proceeding.(Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)1. VISUAL INSPECTIONTurn the ignition off.Visually inspect the Exhaust Differential Pressure Sensor for physical damage, proper electrical connection and proper mechanical connection. Ensure any tubes and/or hoses connected to the sensor are in good working condition and properly connected at all ends.Visually inspect the entire exhaust system for bent, crushed or otherwise damaged tubes which may cause an exhaust system restriction. Inspect the exhaust system for exhaust leaks.Were any problems found?YesRepair or replace as necessary.NoGo To 22. CHECKING THE DIFFERENTIAL PRESSURE SENSOR HOSESTurn the ignition off.Disconnect both Differential Pressure Sensor Hoses at the Differential Pressure Sensor.Apply Low Pressure shop air to each of the disconnected hose ends.The applied air pressure at each hose should flow through the hoses into the DPF Filter.Does the applied air pressure flow through both hoses into the DPF Filter.YesGo To 3NoRepair or replace blocked hoses or DPF Filter connection tubes.(Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)3. EXHAUST DIFFERENTIAL SENSOR CIRCUIT HIGH RESISTANCE

Turn the ignition off.Disconnect the Exhaust Differential Pressure Sensor harness connector.Disconnect the ECM harness connectors.Measure the resistance of each Exhaust Differential Pressure Sensor circuit between the Exhaust Differential Pressure Sensor harness connector and the ECM harness connector.Is the resistance below 10.0 ohms for each circuit?YesGo To 4NoRepair the circuit(s) that measured above 10.0 ohms for high resistance.(Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)4. EXHAUST DIFFERENTIAL PRESSURE SENSORTurn the ignition off.Replace the Exhaust Differential Pressure Sensor.Turn the ignition on.With the scan tool, Clear DTCs in the Engine Control Module (ECM).Test drive the vehicleWith the scan tool, Read DTCs in the Engine Control Module (ECM).Is the status Active for this DTC?YesReplace the Diesel Particulate Filter.NoTest Complete.