Case IH F-4765-01 - ECU – Engine Control Module (ECM) / Engine ECU: Upstream oxidation catalyst temperature sensor voltage is lower than expected

The voltage signal returning from the temperature sensor located just before the Diesel Oxidation Catalyst (DOC) has dropped below the normal operating range. This condition typically points to a short to ground in the wiring, a disconnected line, or an internally failed sensor element.

• MAGNUM AFS Connect
• 240 Series Axial-Flow Combines (7230, 7240, 7250, 9230)
• Farmall 40
• Farmall 45
• Farmall 50
• Farmall 100C
• Farmall 105A
• Farmall 105C
• Farmall 105U
• Farmall 110A
• Farmall 110C
• Farmall 110U
• Farmall 115A
• Farmall 115C
• Farmall 115U
• Farmall 120U
• Maxxum 120
• Maxxum 125
• Maxxum 130
• Maxxum 140
• Maxxum 5130
• Maxxum 5140
• Puma 140
• Magnum 7130
• Magnum 7140
• Magnum 7150

1. 1

   Inspect the wiring harness between the ECM and the upstream DOC temperature sensor for chafing, melting, or a short circuit to ground

2. 2

   Disconnect the sensor and inspect the Bosch 2-pin plug for corrosion or damage

3. 3

   Verify voltage at the connector: Pin 1 should provide a 5-volt reference supply from the ECM, and Pin 2 should provide a common ground to the ECU

1. 1

   Turn off the engine, disconnect the battery, and allow the exhaust system to cool completely to avoid burns.

   Safety precaution before beginning work on the exhaust aftertreatment system.

2. 2

   Locate the upstream DOC temperature sensor on the exhaust aftertreatment system.

   It is positioned on the exhaust pipe just before the Diesel Oxidation Catalyst chamber.

3. 3

   Disconnect the 2-pin electrical connector from the sensor.

   Prepare the sensor for removal.

4. 4

   Carefully unscrew and remove the faulty exhaust gas temperature sensor from the exhaust pipe.

   Use a wrench (typically 17mm for the M14x1.5 thread). Penetrating oil may be required if the sensor is seized from exhaust heat.

5. 5

   Install the new temperature sensor into the exhaust pipe.

   Tighten it to the manufacturer's specified torque.

6. 6

   Reconnect the 2-pin electrical connector.

   Ensure the connection is secure.

7. 7

   Restore battery power, clear the fault codes from the ECM using a diagnostic tool, and run the machine.

   Verify the repair by ensuring the code does not return.