Case IH 3979 – ENGINE ECU: Particulate Matter Catalyst (PMCat) : Signal range check flow resistance of the particulate filter - very high.

The Diesel Particulate Filter (DPF) is severely restricted or completely blocked by an accumulation of soot or ash. The engine control system monitors the exhaust backpressure via a differential pressure sensor, and this code triggers when the flow resistance exceeds the maximum allowable threshold.

• skid steer
• Skid Steer Loaders (SSL)
• Compact Track Loaders (CTL)
• Farmall C series
• Luxxum models

1. 1

   Check for accompanying codes such as 3789 (Regeneration duration exceeds maximum allowed) or 3796 (Diesel particulate filter pressure sensor hose line error)

2. 2

   Physically inspect the hoses running from the exhaust pipe to the DPF differential pressure sensor for blockages (soot buildup), melting, cracks, or disconnected lines

3. 3

   Use the Case IH Electronic Service Tool (EST) to check the calculated soot and ash load percentages (if over 140%, standard regeneration is locked out)

4. 4

   Check for underlying engine issues that cause excessive smoking, such as boost leaks, clogged air filters, or failing fuel injectors

1. 1

   Attempt Manual Regeneration

   Connect the Case IH Electronic Service Tool (EST). If the software permits, initiate a manual/forced stationary regeneration. Caution: Ensure the machine is parked outside away from combustible materials, as the exhaust stack will become extremely hot.

2. 2

   Remove the DPF

   If the EST blocks the forced regeneration due to the filter being too restricted, or if the manual regeneration fails to clear the code, the DPF must be physically removed from the exhaust system.

3. 3

   Clean or Replace the Catalyst

   Send the removed DPF to a certified emissions cleaning facility to have the compacted ash and soot baked and blown out. If the catalyst substrate is cracked, melted, or cannot be cleaned, the DPF assembly must be replaced.

4. 4

   Clear Hoses and Sensor

   Blow out the DPF pressure sensor metal lines and rubber hoses with compressed air to ensure they are completely clear of soot.

5. 5

   Reset ECU Parameters

   Reinstall the cleaned or new DPF. You must use the Case IH EST to tell the Engine ECU that a new or cleaned DPF has been installed. This resets the soot/ash accumulators to zero.

6. 6

   Clear Codes

   Clear the 3979 fault code and run the engine to verify that exhaust backpressure is back within normal operating ranges.