Case IH F-4766-14 - ECU – Engine Control Unit (ECU): Upstream oxidation catalyst temperature sensor comparison to a calculated temperature value failure

The Engine Control Unit (ECU) has detected that the actual exhaust temperature measured by the upstream Diesel Oxidation Catalyst (DOC) temperature sensor differs significantly from the temperature value calculated by the ECU's internal model. This discrepancy typically indicates either a faulty sensor/circuit or an underlying engine performance issue (such as incorrect fuel injection pressure, incorrect injection timing, or an improper Exhaust Gas Recirculation (EGR) rate) that is physically altering the exhaust temperature.

• MAGNUM AFS Connect
• Axial-Flow Combines (240 Series)
• Austoft 9900 Sugarcane Harvesters
• Puma series tractors
• Magnum series tractors
• Steiger series tractors

1. 1

   Check the wiring harness and connectors between the ECU and the upstream DOC temperature sensor for correct isolation, contact, and absence of corrosion

2. 2

   Inspect the exhaust line for any physical leaks upstream of the DOC that could allow heat to escape before reaching the sensor

3. 3

   Verify engine performance parameters (fuel injection pressure, injection timing, and EGR rates) to ensure they are within specification

4. 4

   Execute a service (forced) regeneration and monitor live data to see if the temperature after the DOC increases properly

1. 1

   Safely shut down the machine

   Allow the exhaust system to cool completely to avoid severe burns.

2. 2

   Locate the upstream DOC temperature sensor

   The sensor is threaded into the exhaust piping just before the Diesel Oxidation Catalyst chamber.

3. 3

   Disconnect the sensor harness and check wiring

   Use a multimeter to check for continuity, shorts to ground, or open circuits in the chassis-side wiring leading back to the ECU. Repair the harness if voltage/resistance values are out of specification.

4. 4

   Remove and inspect the temperature sensor

   Use the appropriate wrench to remove the sensor. Inspect the sensor tip for heavy soot fouling or physical damage.

5. 5

   Test the sensor resistance

   Test against OEM specifications. If the sensor is out of range or physically damaged, install a new OEM exhaust temperature sensor.

6. 6

   Address Engine Faults (If Applicable)

   If the sensor and wiring are perfectly functional, the issue lies in the engine's combustion process. Diagnose and repair any secondary codes related to the fuel rail, injectors, or EGR valve.

7. 7

   Reassemble and Clear Codes

   Reconnect the sensor, clear the F-4766-14 fault code via the diagnostic service tool, and run a stationary service regeneration to verify that the sensor reading now matches the ECU's calculated temperature model.