Case IH 3978 – Engine ECU: ENGINE, Particulate Matter Catalyst (PMCat): Signal range check flow resistance of the particulate filter - High.

The engine control system has detected that the exhaust backpressure (flow resistance) across the Diesel Particulate Filter (DPF) is higher than the acceptable range. This is typically caused by excessive soot buildup in the filter, often triggering an ATS Fail message.

• Steiger T4B
• Steiger
• Farmall
• JX series
• SR130
• SR160
• SR210

1. 1

   Verify operating conditions: Check if the machine has been operating at low idle or under light loads for extended periods, which prevents passive regeneration and causes soot face-plugging.

2. 2

   Check for related codes: Look for codes 3428 or 3429, which indicate a failure or implausible reading from the DPF Differential Pressure Sensor or its hoselines.

3. 3

   Inspect sensor hoses: Physically inspect the differential pressure sensor hoses connecting the DPF to the sensor. Look for melting, cracking, or blockages (soot/ice) that could cause a false high resistance reading.

1. 1

   Perform a Forced/Manual Regeneration

   The primary OEM repair procedure for code 3978 is to initiate a manual (parked) regeneration of the particulate catalytic converter.

2. 2

   Safety Prep

   Park the machine in a safe, well-ventilated area away from combustible materials. The operator's manual warns that the exhaust stack and fixed hood area will become extremely hot during this process.

3. 3

   Initiate Regen

   Use the instrument cluster or the dealer Electronic Service Tool (EST) to command the forced regeneration. The ECU will elevate engine RPMs and inject fuel into the exhaust to burn off the soot.

4. 4

   Monitor Progress

   Allow the cycle to complete (the dash will usually show a progress bar up to 100%).

5. 5

   Post-Regen Check

   If the code clears, instruct the operator to run the machine at higher RPMs during normal use. If the code persists or the ECU blocks regeneration, the DPF differential pressure sensor must be replaced, or the DPF itself must be removed and sent to a specialized facility for ash cleaning/baking.