New Holland ENG 3993 – Engine ECU: Diesel Particulate Filter (DPF) IN Temperature is over 800 °C (1472 °F)

This indicates that the exhaust gas temperature entering the DPF has exceeded the critical threshold of 800 °C. This condition can be caused by a faulty temperature sensor reading artificially high, or an actual over-temperature event caused by excessive soot accumulation, a post-injection failure, or uncontrolled burning (thermal runaway) inside the DPF.

• L213
• L215
• L216
• L218
• L220
• L221
• L223
• L225
• L313
• L316
• L318
• L320
• C227
• C238
• C245
• SR130
• SR150
• SR160
• SR175
• SV185
• TR series
• TV series
• B90B
• B100B

1. 1

   Connect the electronic service tool (EST) and view the FT4 Data Monitoring parameters. Check the value and graph for the DPF IN Temperature sensor (exhaust gas temp sensor #2).

2. 2

   Check the sensor reading on a cold engine. If the sensor reads artificially high (e.g., near or over 800 °C) while the engine is cold, the sensor or its circuit is shorted/faulty.

3. 3

   Check for related voltage fault codes (such as Out of Voltage - High or Out of Voltage - Low), which indicate a short circuit or wiring harness issue.

4. 4

   Inspect the sensor wiring and connector for corrosion, melting, or chafing.

5. 5

   If the sensor is reading accurately, inspect the DPF for premature clogging or soot over-deposition, which can cause dangerous exhaust temperature spikes during regeneration.

1. 1

   Prepare machine

   Turn off the machine, disconnect the battery, and ensure the exhaust system has completely cooled down to prevent severe burns.

2. 2

   Locate the sensor

   Locate the DPF IN temperature sensor (exhaust gas temp sensor #2) on the inlet side of the Diesel Particulate Filter assembly.

3. 3

   Remove the sensor

   Disconnect the sensor's electrical connector. Use a crowfoot wrench to loosen the temperature sensor tightening nut to prevent damaging the sensor or surrounding differential pressure pipes. If the sensor is seized due to high exhaust heat, apply a penetrating lubricant spray to the threaded portion and allow it to soak before attempting to loosen it.

4. 4

   Install new sensor

   Thread the new OEM temperature sensor into the DPF inlet housing. Torque the sensor to the manufacturer specification (40.50 - 49.50 N·m or 29.87 - 36.51 lb ft).

5. 5

   Reassemble and route wiring

   Reconnect the sensor wiring harness. Ensure the wiring is routed away from the hot DPF housing to prevent future melting.

6. 6

   Clear codes and test

   Reconnect the battery. Use a diagnostic tool or DTC eraser to clear the ENG 3993 code from the Engine ECU. Run the machine and monitor the DPF IN temperature to verify it reads ambient temperature on startup and rises normally under load.

7. 7

   Perform DPF service (if applicable)

   If the old sensor was reading correctly and the DPF was actually overheating (actual over-temperature cause), you must perform a manual/service regeneration or remove the DPF for professional ash cleaning/replacement to prevent a fire hazard.