Case IH 3981 – Engine ECU: DOC-In temperature under 220 deg C during regeneration

The exhaust gas temperature at the inlet of the Diesel Oxidation Catalyst (DOC) is failing to reach the minimum required threshold of 220°C (428°F) during an active regeneration cycle. This minimum temperature is critical because it is required to initiate the catalytic reaction that burns off accumulated soot in the Diesel Particulate Filter (DPF).

• skid steer
• Small and medium frame Skid Steer Loaders
• SR175
• SV250
• SV300
• Compact Track Loaders
• TR320
• TV380
• Compact and Utility Tractors
• Farmall series
• Boomer series

1. 1

   Verify the DOC inlet temperature sensor (B-9001 or exhaust gas temp sensor #1) for proper operation, as a faulty sensor can report artificially low temperatures.

2. 2

   Inspect the exhaust piping between the engine turbocharger/manifold and the DOC for any leaks causing heat loss.

3. 3

   Check the intake air system for leaks that could disrupt the air-to-fuel ratio and lower exhaust temperatures.

4. 4

   Check the aftertreatment burner injectors or late-cycle fuel dosing system to ensure fuel is being injected into the exhaust stream.

5. 5

   Inspect the DOC itself for face plugging, heavy soot accumulation, or physical degradation.

1. 1

   Test the Sensor

   Connect a diagnostic service tool and monitor the live data for the DOC inlet temperature sensor. Compare the reading to the ambient temperature when the engine is completely cold. If the reading is erratic, out of range, or stuck, replace the DOC inlet temperature sensor.

2. 2

   Inspect and Seal Exhaust

   Perform a visual and audible inspection of the exhaust piping and clamps. Tighten any loose clamps and replace blown gaskets if exhaust leaks are found.

3. 3

   Test the Dosing System

   If the sensor and exhaust system are intact, use the diagnostic tool to initiate a forced (manual) regeneration. Monitor the DOC inlet temperature to see if it climbs toward the 220°C (428°F) threshold. If it fails to rise, inspect the fuel dosing system (burner injector) for clogs or electrical faults (check for related codes like 3989 or 3990). Clean or replace the doser/injector as necessary.

4. 4

   Inspect the DOC/DPF Assembly

   If all upstream components (sensor, exhaust integrity, fuel dosing) are functioning correctly, the DOC itself may be degraded or face-plugged.

5. 5

   Remove the DOC

   Remove the exhaust clamp securing the inlet pipe. Support the DPF/DOC assembly with a suitable lifting device, remove the mounting bolts, and remove the assembly to inspect the catalyst face.

6. 6

   Replace and Verify

   If the DOC is damaged or heavily plugged, replace the DOC assembly. Clear the fault codes and perform a successful stationary regeneration to verify the repair.