Case IH 3791 – Engine Control Unit (ECU): Diesel Particulate Filter (DPF): Diagnostic fault check for SRC high in Flow Resistance.

The Engine Control Unit has detected that the flow resistance (backpressure) across the Diesel Particulate Filter is excessively high. The DPF Differential Pressure Sensor is reading a pressure drop that indicates the filter is severely restricted, usually because it is overloaded with stored soot or ash.

• skid steer
• Steiger
• Magnum
• Maxxum
• Farmall
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• SR175
• SR250
• L220

1. 1

   Inspect the DPF Differential Pressure Sensor Hoses for melting, cracking, detachment, or blockages.

2. 2

   Inspect the wiring harness and connector at the DPF Differential Pressure Sensor for corrosion, chafing, or loose pins.

3. 3

   Check for accompanying DPF codes such as 3786, 3787, or 3790 to confirm the filter is physically plugged.

4. 4

   Use the CNH Electronic Service Tool (EST) to monitor the DPF differential pressure with the engine off (should read zero) and while running, comparing the calculated soot mass against the measured flow resistance.

1. 1

   Repair or replace sensor or lines

   If the diagnostic checks reveal melted or blocked differential pressure hoses, or a faulty sensor, replace the damaged components first.

2. 2

   Attempt forced regeneration

   If the sensor and lines are intact, connect the CNH EST diagnostic tool and attempt to command a manual/forced stationary DPF regeneration to burn off the accumulated soot.

3. 3

   Clean or replace the DPF

   If the soot/ash load is too high (often indicated if the ECU locks out regeneration to prevent a fire), or if the forced regeneration fails to lower the flow resistance, the DPF must be removed from the machine and sent to a specialized facility to be baked and blown out (ash cleaning) or replaced entirely.

4. 4

   Reset ECU parameters

   After cleaning or replacing the DPF, you must use the diagnostic service tool to reset the DPF soot/ash load timers and clear the fault codes. If this step is skipped, the ECU will still assume the filter is clogged.