Case IH 3953 – Engine ECU: Exhaust Gas Temperature 2 Sensor Signal Too High

The Engine Control Unit (ECU) is detecting a voltage signal from the Exhaust Gas Temperature (EGT) Sensor 2 that exceeds the maximum expected physical range. This plausibility check failure indicates the sensor reading disagrees with another temperature sensor, usually pointing to a short circuit to power, a damaged wiring harness, or a failed sensor.

• Farmall 100C
• Farmall 105A/C/U
• Farmall 110A/C/U
• Farmall 115A/C/U
• Farmall 120U
• Maxxum 110
• Maxxum 120
• Maxxum 125
• Maxxum 130
• Maxxum 140
• Puma 140
• Steiger
• Magnum
• Combine 5130
• Combine 5140
• Combine 7130
• Combine 7140
• Combine 7150
• Combine 7230
• Combine 7240
• Combine 7250
• Combine 9230
• SR130
• SR160
• SR175
• L220

1. 1

   Allow the machine to cool completely, as the exhaust and aftertreatment system (DOC/DPF) reach extremely high temperatures (over 1200°F) during operation.

2. 2

   Locate EGT Sensor 2 on the exhaust aftertreatment system and visually inspect the sensor body, the 2-pin electrical connector, and the wiring harness for melting, chafing, or physical damage.

3. 3

   Disconnect the sensor and use a multimeter to check the harness side for a short to battery/power, which is the primary trigger for a 'Signal Too High' code.

4. 4

   Use a diagnostic scan tool to view live data for all Exhaust Gas Temperature sensors with the engine cold. If EGT Sensor 2 reads significantly higher than ambient temperature while the others read normally, the sensor is internally shorted and must be replaced.

1. 1

   Preparation

   Turn off the engine, remove the key, and ensure the exhaust system is cool to the touch.

2. 2

   Disconnect

   Unplug the 2-pin electrical connector from the faulty Exhaust Gas Temperature 2 Sensor.

3. 3

   Removal

   Using a wrench (typically 17mm for the M14x1.5 thread), carefully loosen and remove the sensor from the exhaust pipe/DPF housing. Note: If the sensor is seized, apply penetrating oil and allow it to soak to prevent stripping the exhaust bung threads.

4. 4

   Installation

   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 in by hand to prevent cross-threading, then tighten to the OEM torque specification.

5. 5

   Reconnect

   Plug the 2-pin connector back into the engine wiring harness. Ensure the locking tab clicks into place and route the wire away from direct heat sources.

6. 6

   Clear Codes

   Turn the key on. Use a diagnostic tool to clear the inactive fault code from the Engine ECU, or run the machine through a standard drive/heat cycle to allow the ECU to recognize the plausible temperature reading and move the code to an inactive state.