Case IH 3685 – EDC (Electronic Diesel Control): Exhaust temperature : Fault Check for enhanced SRC-Min of Second exhaust gas temperature

The control module has detected that the signal from the second exhaust gas temperature sensor is reading below the physically plausible minimum range (SRC-Min). This is typically caused by an internally failed sensor, an open circuit in the wiring harness, or a severe exhaust leak preventing heat from reaching the sensor.

• Farmall (100C–140A)
• Maxxum (120–150)
• Puma (130–240)
• Optum (270–300)
• Steiger
• Quadtrac (350–620)
• Axial-Flow series (5130, 5140, 7130, 7140, 7240, 9230, 9240, 9250, etc.)
• Case CE wheel loaders and backhoes

1. 1

   Live Data Monitoring: Connect a diagnostic scan tool and view the live data for the 'Second Exhaust Gas Temperature.' If the reading is statically stuck at an implausibly low temperature regardless of engine operation, the circuit is open or the sensor is dead.

2. 2

   Visual Inspection: Inspect the wiring harness leading to the second exhaust gas temperature sensor (located in the exhaust aftertreatment module, typically downstream of the DOC or near the DPF/SCR). Look for chafed wires, melted insulation, or a disconnected/corroded plug.

3. 3

   Resistance Test: Disconnect the sensor and measure its resistance with a multimeter. An open reading (infinite resistance/OL) confirms the sensor has failed internally and must be replaced.

4. 4

   Exhaust Leak Check: Inspect the exhaust piping upstream of the sensor for major cracks or blown gaskets that could be venting hot exhaust gases before they reach the sensor.

1. 1

   Safety First

   Ensure the machine is turned off, the key is removed, and the exhaust system has completely cooled to prevent severe burns.

2. 2

   Locate the Sensor

   Find the second exhaust gas temperature sensor on the exhaust aftertreatment assembly.

3. 3

   Disconnect Wiring

   Carefully unplug the electrical connector from the sensor harness.

4. 4

   Remove the Sensor

   Spray the base of the sensor with penetrating oil if it appears rusted or seized. Use a specialized sensor socket or a line wrench to carefully unthread the sensor from the exhaust bung.

5. 5

   Prepare the New Sensor

   Apply a small amount of high-temperature anti-seize compound to the threads of the new sensor (if it does not already come pre-applied from the factory). Note: Do not get anti-seize on the sensor probe itself.

6. 6

   Installation

   Thread the new sensor into the exhaust bung by hand to prevent cross-threading, then tighten it to the OEM torque specification.

7. 7

   Reconnect

   Plug the electrical connector back into the machine's wiring harness, ensuring it clicks securely into place.

8. 8

   Clear Codes

   Turn the key on, use your diagnostic tool to clear fault code 3685, and start the engine. Monitor the live data to ensure the new sensor is reading rising exhaust temperatures accurately.