Case IH 3954 – Engine Control Unit (ECU) - ISM-DI (Perkins) or F5C: Exhaust Gas Temperature 2 Sensor Signal Too Low

The Engine ECU is receiving a voltage signal from the Exhaust Gas Temperature (EGT) Sensor 2 that has fallen below the minimum acceptable threshold, typically pointing to an electrical fault such as an open circuit, a short to ground in the sensor's wiring harness, or a completely failed/internally shorted sensor.

• skid steer
• SR175
• SV185
• TR270
• Farmall 100C
• Farmall 105A
• Farmall 105C
• Farmall 105U
• Farmall 110A
• Farmall 110C
• Farmall 110U
• Farmall 115A
• Farmall 115C
• Farmall 115U
• Farmall 120U
• Maxxum 120
• Maxxum 125
• Maxxum 130
• Maxxum 140
• Puma 140
• 5130
• 5140
• 7130
• 7140
• 7150
• 7230
• 7240
• 7250
• 9230

1. 1

   Inspect the wiring harness leading to EGT Sensor 2 for melted wires, chafing, or physical damage caused by the high heat of the exhaust system.

2. 2

   Disconnect the 2-pin Bosch connector at the sensor and check for water intrusion, corrosion, or pushed-back pins.

3. 3

   Use a multimeter to check for a short to ground or an open circuit in the signal wire between the sensor connector and the Engine ECU.

4. 4

   Check for related codes (such as 3953: Exhaust Gas Temperature 2 Sensor Signal Too High) which can confirm a wiring harness issue versus a hard sensor failure.

1. 1

   Ensure the machine is turned off and the exhaust system (DOC/DPF) has completely cooled down to prevent severe burns.

2. 2

   Locate EGT Sensor 2 on the exhaust aftertreatment piping.

3. 3

   Unplug the 2-pin electrical connector from the machine's wiring harness.

4. 4

   Using a 17mm wrench, carefully loosen and remove the sensor from the exhaust pipe.

   Note: Because exhaust sensors are subjected to extreme heat cycles, penetrating oil may be required to prevent stripping the M14x1.5 mounting threads.

5. 5

   Thread the new EGT sensor into the exhaust bung by hand to prevent cross-threading, then tighten to the manufacturer's specified torque.

6. 6

   Plug the 2-pin connector back into the engine wiring harness.

7. 7

   Connect a diagnostic service tool to clear the 3954 fault code.

   Run the engine and, if required, initiate a manual/service DPF regeneration to verify that the sensor is reading temperatures correctly and the code does not return.