Case IH 17933 (F-4781-00) - ECU – Engine ECU: Maximum catalyst soot mass exceeded

The Diesel Particulate Filter (DPF) has accumulated a level of soot that surpasses the maximum allowable safe limit programmed into the system. When this occurs, the filter is severely restricted, and the system will typically derate the engine to prevent catastrophic damage or a thermal event (exhaust fire).

• VESTRUM CVX
• Farmall Series (40-45-50 CVT, 115U, 85A through 115C)
• Combines (5140)
• Various other Case IH / New Holland tractors and machinery utilizing the MTA CCM & APH Stage V MR on-board diagnostics system

1. 1

   Check operating history to determine if the tractor has been subjected to prolonged idling or low-load operations, which prevents passive regenerations.

2. 2

   Inspect the DPF differential pressure sensor and its connecting tubes/hoses for blockages, melting, or cracking.

3. 3

   Check for upstream engine issues (boost leaks in charge air cooler hoses, a sticking EGR valve, or faulty fuel injectors) that could cause the engine to run rich and over-produce soot.

4. 4

   Use the CNH Electronic Service Tool (EST) to view the live data for the calculated soot mass and the differential pressure sensor voltage.

1. 1

   Attempt a forced regeneration

   Connect the CNH EST diagnostic tool. If the soot mass is above the normal threshold but has not yet crossed the critical point, use the software to command a forced (parked) regeneration.

2. 2

   Remove the DPF

   If the soot mass is critically high, the ECU will lock out the regeneration process entirely to prevent the DPF from melting or catching fire. In this case, physically remove the DPF from the exhaust stream.

3. 3

   Clean or replace the DPF

   Send the removed DPF to a certified facility to be professionally baked and blown out (ash/soot cleaning), or replace it with a new or remanufactured unit.

4. 4

   Replace sensors

   If the differential pressure sensor or its tubes are clogged with soot, replace them to ensure accurate readings moving forward.

5. 5

   Reset the ECU accumulator

   Once the clean or new DPF is installed, you must use the CNH EST to reset the DPF soot mass accumulator / ash counter in the Engine ECU. If skipped, the ECU will maintain the engine derate.

6. 6

   Clear codes and test

   Clear the 17933 fault code, start the engine, and run the machine under a heavy load to verify that the exhaust differential pressure remains within normal specifications.