Case IH 3684 – Engine Control Module (ECM): Exhaust temperature : Fault Check for enhanced SRC-Max of Second exhaust gas temperature

The Engine Control Module has detected that the signal from the second exhaust gas temperature sensor (Sensor 2, located downstream of the DOC/DPF or SCR) is reading higher than the maximum expected value during a Signal Range Check (SRC-Max). This typically indicates a short circuit to voltage, a failed sensor, or an actual over-temperature condition in the exhaust system.

• Axial-Flow Combines 7230
• Axial-Flow Combines 8230
• Axial-Flow Combines 9230
• Maxxum Tractors 110
• Maxxum Tractors 120
• Maxxum Tractors 125
• Maxxum Tractors 130
• Maxxum Tractors 140
• Puma Tractors 140
• Farmall Tractors 100C
• Farmall Tractors 105U
• Farmall Tractors 115U
• Steiger / Magnum Series

1. 1

   Visual Inspection: Check the wiring harness and the 2-pin connector for Exhaust Gas Temperature Sensor 2 for chafing, melting, or corrosion.

2. 2

   Live Data Monitoring: Use a diagnostic scan tool to monitor the live data for Exhaust Gas Temperature Sensor 2. If the sensor reads an impossibly high value (e.g., maximum voltage/temperature) when the engine is cold, the sensor is likely shorted internally or there is a short to power in the harness.

3. 3

   Resistance Test: Disconnect the sensor and perform a resistance check using a multimeter to verify if the sensor itself is shorted or open.

4. 4

   Check for Related Codes: Look for other active exhaust temperature or DPF/SCR related codes (such as 3685, 3686, or 3687) which might indicate a broader harness issue or an actual exhaust system overheating event (e.g., a stuck doser valve).

1. 1

   Cool exhaust system

   Turn off the engine and allow the exhaust system to cool completely to avoid severe burns.

2. 2

   Disconnect battery

   Disconnect the negative battery terminal to prevent electrical shorts.

3. 3

   Locate sensor

   Locate Exhaust Gas Temperature Sensor 2. This is the downstream sensor, typically located after the Diesel Oxidation Catalyst (DOC), Diesel Particulate Filter (DPF), or SCR unit.

4. 4

   Disconnect connector

   Disconnect the 2-pin electrical connector for the sensor.

5. 5

   Apply penetrating oil

   Spray penetrating oil on the sensor threads and allow it to sit, as exhaust sensors are highly prone to seizing.

6. 6

   Remove sensor

   Using a suitable wrench (often 15mm or 17mm depending on the specific engine/sensor), carefully unscrew the sensor from the exhaust pipe or manifold.

7. 7

   Apply anti-seize

   Apply a small amount of high-temperature anti-seize compound to the threads of the new sensor (if not already pre-applied by the manufacturer). Be extremely careful not to get any anti-seize on the sensor probe itself.

8. 8

   Install new sensor

   Install the new sensor and tighten it to the manufacturer's specified torque.

9. 9

   Reconnect connector

   Reconnect the electrical connector, ensuring it clicks securely into place.

10. 10

    Clear fault code and verify

    Reconnect the battery, start the engine, and use a diagnostic tool to clear the 3684 fault code. Verify that the live temperature reading is now within the normal operating range.