New Holland ENG 3953 – Engine Control Unit (ECU): Exhaust Gas Temperature 2 Sensor Signal Too High

The Engine Control Module (ECM) has detected a high signal voltage at the Exhaust Gas Temperature #2 sensor circuit. This sensor (also referred to as the catalyst outlet temperature sensor) monitors the engine exhaust temperature entering or exiting the catalyst unit. A 'Signal Too High' condition typically points to a short circuit to a high-voltage source, a damaged wiring harness, or an internally shorted sensor.

• L218
• L220
• L228
• L316
• L318
• L320
• SR130
• SR160
• SR175
• W170B
• W190B

1. 1

   Locate the Sensor: Find the Exhaust Gas Temperature 2 sensor in the aftertreatment system. It is generally located in the exhaust stream between the turbocharger outlet and the catalyst unit outlet. Note: The ECM diagnostic for this sensor only runs when the engine coolant temperature is above 140°F (60°C).

2. 2

   Visual Inspection: Inspect the sensor's 2-pin electrical connector and the associated wiring harness. Look for rubbed wires, melted insulation, or corrosion that could cause a short to a high-voltage source.

3. 3

   Voltage/Resistance Test: Disconnect the sensor and use a multimeter to check the harness for a short to battery voltage. Test the sensor's internal resistance to see if it is out of specification (shorted internally).

4. 4

   Live Data Check: If you have a diagnostic service tool, monitor the Exhaust Gas Temperature 2 live data. If the temperature reading is erratic, stuck at a maximum value, or not changing with engine operating conditions, the sensor is likely faulty.

1. 1

   Preparation

   Turn off the machine, remove the key, and disconnect the battery to prevent electrical spikes during the repair. Ensure the exhaust system has completely cooled down to prevent severe burns.

2. 2

   Disconnect

   Locate the Exhaust Gas Temperature 2 sensor on the aftertreatment exhaust pipe and unplug its 2-pin electrical connector.

3. 3

   Harness Repair

   If the diagnostic checks revealed a short in the wiring harness, repair or splice the damaged section of the wire and secure it away from extreme heat sources.

4. 4

   Sensor Removal

   If the wiring is intact, use an appropriate wrench or sensor socket to carefully unthread the faulty temperature sensor from the exhaust bung. (Penetrating oil may be required if the sensor is seized from exhaust heat).

5. 5

   Installation

   Apply a small amount of anti-seize compound to the threads of the new sensor (avoiding the sensor probe tip). Thread the new sensor into the exhaust bung and tighten to the OEM torque specification.

6. 6

   Reassembly

   Reconnect the 2-pin electrical connector. Reconnect the machine's battery.

7. 7

   Validation

   Start the engine and allow it to warm up until the engine coolant temperature exceeds 140°F (so the ECM can run its internal diagnostic). Use a diagnostic service tool to clear the ENG 3953 fault code and verify that the code does not return and that the live temperature data is reading accurately.