New Holland 3686 – ECM: EGTS 1 Cold Start Condition Fault

The Engine Control Module (ECM) has detected a signal drift or an implausible reading from Exhaust Gas Temperature Sensor 1 (EGTS 1) during a cold start condition. The sensor, located upstream of the Diesel Oxidation Catalyst (DOC) or Diesel Particulate Filter (DPF), is sending a voltage signal that does not align with expected ambient or cold-engine temperature parameters. This typically indicates a failure of the sensor's internal resistance or a wiring fault.

• New Holland tractors and agricultural equipment with FPT / Iveco NEF engines (Tier 3
• Tier 4A
• Tier 4B
• Stage V)

1. 1

   Connect the CNH Electronic Service Tool (EASy tool) to confirm that DTC 3686 is active

2. 2

   Inspect the wiring harness and the electrical connector for Exhaust Gas Temperature Sensor 1 for melted wires, chafing, or corrosion that could cause a short circuit to ground or battery voltage

3. 3

   Use a multimeter to check the sensor's resistance and voltage output; an open circuit or a voltage reading stuck above 5.2V indicates a faulty sensor or wiring

4. 4

   Check the sensor probe for severe physical damage or excessive soot buildup that could insulate the probe and cause delayed or inaccurate readings

1. 1

   Preparation

   Turn off the equipment, disconnect the battery, and ensure the exhaust system has completely cooled down to prevent severe burns.

2. 2

   Locate the sensor

   Locate Exhaust Gas Temperature Sensor 1, which is threaded into the exhaust pipe upstream of the DOC (Diesel Oxidation Catalyst) / DPF assembly.

3. 3

   Disconnect wiring

   Unplug the sensor's electrical connector from the main engine wiring harness.

4. 4

   Remove the sensor

   Carefully unscrew the sensor from the exhaust pipe. Apply penetrating oil to the threads prior to removal to avoid stripping the exhaust bung, as EGTS sensors are prone to seizing due to high heat.

5. 5

   Install new sensor

   Thread the new Exhaust Gas Temperature Sensor into the exhaust pipe and tighten it to the manufacturer's specified torque.

6. 6

   Reconnect wiring

   Plug the new sensor's pigtail cable back into the engine wiring harness.

7. 7

   Clear code and verify

   Reconnect the battery. Use the CNH EASy diagnostic tool to clear fault code 3686. Start the engine and perform a powertrain verification test to ensure the ECU reads the exhaust temperature correctly and the code does not return.