Case IH 3687 – Engine ECU / EDC (Electronic Diesel Control): Exhaust temperature : Fault check for cold start condition of exhaust-gas temperature sensor 2.

This code indicates a plausibility error or signal drift detected by the system during a cold start. When the engine is cold, the exhaust gas temperature sensors should read close to ambient temperature. The system compares Exhaust Gas Temperature (EGT) Sensor 2 against other temperature sensors (like EGT Sensor 1 or ambient air temp). If Sensor 2 reports a temperature that is significantly out of range compared to the baseline cold-start conditions, this fault is triggered.

• Farmall series (100C, 105A, 105C, 105U, 110A, 115U, 120U, etc.)
• Maxxum series (120, 125, 130, 140)
• Puma series
• Magnum series
• 240 Series Combines

1. 1

   Connect a diagnostic scan tool after the machine has been sitting overnight (cold engine) and compare EGT Sensor 2 live data against EGT Sensor 1 or ambient temperature to check for sensor drift

2. 2

   Inspect the wiring harness leading to EGT Sensor 2 for chafed wires, melted insulation from exhaust heat, or loose/corroded pins at the connector

3. 3

   Perform a circuit test to verify that the sensor is receiving the correct reference voltage and has a solid ground from the EDC

1. 1

   Safety First

   Ensure the machine is turned off and the exhaust/aftertreatment system has completely cooled down to prevent severe burns.

2. 2

   Locate the Sensor

   Locate Exhaust Gas Temperature Sensor 2. Depending on the specific emissions setup (DOC/DPF/SCR), this is typically threaded into the exhaust pipe after the turbocharger or within the diesel particulate filter/catalyst housing.

3. 3

   Disconnect

   Unplug the electrical connector for the sensor.

4. 4

   Removal

   Use a wrench (often 17mm) to unscrew the sensor from the exhaust bung. Note: Exhaust sensors frequently seize due to extreme heat cycles. Apply penetrating oil and allow it to soak if the sensor is stuck.

5. 5

   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 manufacturer's specified torque.

6. 6

   Reconnect

   Plug the electrical connector back into the engine harness.

7. 7

   Clear Codes

   Use a diagnostic tool to clear the 3687 fault code from the EDC memory. Perform a cold start to verify the code does not return.