New Holland ENG 3791 – Engine Control Unit (ECU / EDC7): Diesel Particulate Filter (DPF): Diagnostic fault check for SRC high in Flow Resistance

This code indicates that the Engine Control Unit (ECU) has detected an abnormally high flow resistance (restriction) across the Diesel Particulate Filter. The differential pressure sensor is reporting that the exhaust backpressure is too high, which typically means the DPF is severely clogged with accumulated soot/ash, or there is a malfunction in the differential pressure sensor circuit.

• T7
• T8 (Genesis)
• T9 Series
• Workmaster series
• CR9090
• CX8080 Elevation
• CX8090 Elevation
• Telehandlers & Loaders with FPT engines

1. 1

   Check operating conditions to determine if the machine has been doing a lot of stop-and-go work or idling, which prevents passive DPF regeneration

2. 2

   Visually inspect the two metal/rubber lines running from the DPF housing to the DPF Differential Pressure Sensor for cracks, melting, blockages (carbon buildup), or disconnected hoses

3. 3

   Check the wiring harness and connector to the DPF differential pressure sensor for corrosion or damage

4. 4

   Connect a diagnostic scan tool to read live data for the DPF soot load percentage and the live differential pressure sensor voltage/pressure readings

1. 1

   Clear Sensor Lines

   If the differential pressure sensor lines are clogged with soot, remove them and blow them out with compressed air. Reinstall and re-check pressure readings.

2. 2

   Perform a Forced Regeneration

   If the sensor and lines are intact and the scan tool shows a high soot load, initiate a stationary Forced Regeneration via the diagnostic software. The machine must be parked in a safe, well-ventilated area. The ECU will elevate the engine RPM and inject fuel to raise exhaust temperatures to burn off the soot.

3. 3

   Replace the Sensor

   If the sensor readings are erratic, stuck high even when the engine is off, or fail to change during operation, replace the DPF Differential Pressure Sensor.

4. 4

   Clean or Replace the DPF

   If the forced regeneration fails, is locked out by the ECU due to excessive soot mass, or if the filter is face-plugged with incombustible ash, the DPF must be physically removed. It will need to be sent to a specialized facility for pneumatic/thermal ash cleaning or replaced entirely.

5. 5

   Clear Codes

   After the repair or regeneration is complete, use the diagnostic tool to clear the ENG 3791 fault code and reset the DPF soot accumulation counter if the filter was replaced or cleaned.