New Holland ENG 3951 – ENGINE ECU: Exhaust Gas Temperature 1 Sensor - Signal Too High

The engine control module is receiving a voltage signal from the Exhaust Gas Temperature (EGT) 1 sensor that exceeds the maximum expected threshold. A "Signal Too High" condition typically indicates an open circuit in the sensor itself, a broken wire in the harness, a disconnected plug, or a short to a voltage source.

• L216 Tier 4
• L218
• L220
• L228
• Super Boom L180
• SR175
• C227
• C232
• C238

1. 1

   Use the New Holland Service Tool to confirm that ENG 3951 is currently active and check for any accompanying codes related to the DPF/DOC or EGR system.

2. 2

   Inspect the wiring harness from the Engine ECU to the Exhaust Gas Temperature 1 Sensor connector for physical damage, corrosion, abrasion, or incorrect attachment.

3. 3

   Disconnect the EGT 1 sensor and inspect the pins on both the sensor side and the harness side for bent pins, pushed-out terminals, or moisture/corrosion.

4. 4

   Test the sensor's internal resistance with a multimeter to determine if the sensor itself has an open circuit.

5. 5

   Test the harness for continuity back to the ECU and test for a short to power (voltage).

1. 1

   Safety First

   Turn off the machine, remove the key, and attach a "Do Not Operate" tag. Allow the engine and exhaust system to cool down completely.

2. 2

   Locate the Sensor

   Locate the Exhaust Gas Temperature 1 Sensor. It is typically threaded into the exhaust stream upstream of the Diesel Oxidation Catalyst (DOC) / Diesel Particulate Filter (DPF) or on the intake of the middle part of the filter housing.

3. 3

   Disconnect

   Unplug the electrical connector from the EGT sensor.

4. 4

   Remove the Sensor

   Carefully unscrew the failed EGT sensor from the exhaust housing using the appropriate wrench. (Penetrating oil may be required if the sensor is seized from heat cycling).

5. 5

   Install the New Sensor

   Apply a small amount of high-temperature anti-seize compound to the threads of the new sensor (if it does not come pre-applied). Thread the new sensor into the exhaust housing and tighten to OEM torque specifications.

6. 6

   Reconnect

   Plug the electrical connector back into the sensor harness, ensuring it clicks securely into place.

7. 7

   Clear and Verify

   Reconnect the diagnostic Service Tool, clear the ENG 3951 fault code, and run the engine. Monitor the live exhaust gas temperature data to verify the sensor is reading correctly and the fault does not return.