Case IH 3686 – EDC (Electronic Diesel Control) / ECU: Exhaust temperature : Fault for cold start condition of exhaust-gas temperature sensor 1

The upstream exhaust gas temperature (EGT) sensor is providing an implausible reading during a cold engine start. During a cold start, the engine control module expects the exhaust temperature sensor to read very close to the ambient air temperature or engine coolant temperature. If the sensor reports a value that is significantly out of this expected range, the system flags it as a cold start condition fault.

• Farmall 100C
• Farmall 105A
• Farmall 110A
• Farmall 115A
• Farmall 120U
• Maxxum 120
• Maxxum 125
• Maxxum 130
• Maxxum 140
• Puma series
• Combine harvesters

1. 1

   Cold Soak Temperature Comparison: Using a diagnostic scan tool, monitor the live data for 'Exhaust Gas Temperature Sensor 1' (upstream) after the machine has been sitting overnight (cold soak). Compare this reading to the ambient air temperature and engine coolant temperature. If the EGT sensor reading is drastically different from the others, the sensor is faulty.

2. 2

   Visual Inspection: Inspect the wiring harness and the connector leading to the upstream EGT sensor (located on the exhaust pipe before the aftertreatment/DPF system). Look for melted wires, chafing, or corrosion in the pins.

3. 3

   Circuit Testing: Check the sensor circuit for proper reference voltage and ensure there are no open circuits or short-to-ground conditions in the harness between the sensor and the EDC.

1. 1

   Turn the master electric switch (battery disconnect) to the "OFF" position.

   Ensure the machine's electrical system is powered down before beginning the repair.

2. 2

   Locate the upstream exhaust gas temperature sensor (Sensor 1).

   It is typically positioned on the exhaust pipe before the Diesel Particulate Filter (DPF) or Diesel Oxidation Catalyst (DOC).

3. 3

   Disconnect the sensor's electrical connector.

   Unplug the connector from the engine wire harness.

4. 4

   Carefully unscrew and remove the sensor from the exhaust pipe.

   OEM Warning: Do not use impact wrenches on the exhaust system unless the sensors are already removed, as this can damage sensitive aftertreatment components.

5. 5

   Install the new temperature sensor.

   Thread the new sensor into the exhaust pipe.

6. 6

   Torque the sensor.

   Tighten the sensor to 40 to 50 Nm (30 to 36 lb-ft).

7. 7

   Reconnect the sensor to the wire harness.

   Secure the harness to the support brackets using new wire ties to prevent vibration damage.

8. 8

   Verify the repair.

   Turn the master electric switch back on, clear the fault codes using your diagnostic tool, and start the engine to verify the repair.