Case IH F-3222-12 - ECU – Engine Control Unit (ECU): Upstream NOx sensor internal failure (Heater Performance Plausibility Error)

The upstream NOx sensor relies on an internal heating element to reach a specific operating temperature. A Heater Performance Plausibility Error means the system has detected abnormal resistance, a short circuit, or an open circuit in the heater element, preventing the sensor from reaching or maintaining the required temperature.

• MAGNUM AFS Connect
• 240 Series Axial-Flow Combines
• Austoft 9900 Sugarcane Harvesters
• Steiger
• Magnum
• Puma
• Farmall

1. 1

   Check battery voltage and alternator output, as high or low voltage can trigger heater plausibility errors during cold starts

2. 2

   Inspect the wiring harness and connector C186 leading to the upstream NOx sensor for defects, high resistance, or physical damage

3. 3

   Test the heater circuit for a short to ground or an open circuit

4. 4

   Verify there are no accompanying CAN timeout errors (e.g., code 19060) indicating a broader communication failure between the sensor and the ECU

1. 1

   Cool Down

   Ensure the machine is turned off and the exhaust system has completely cooled, as the upstream NOx sensor is located in a high-heat area before the DOC.

2. 2

   Disconnect

   Locate the upstream NOx sensor and disconnect its 5-cavity female wire connector (C186).

3. 3

   Inspect

   Check the presence and correct connection of the pins/terminals. If the wiring harness is defective, repair the wiring.

4. 4

   Remove

   If the wiring is intact, the internal heater has failed. Use the appropriate sensor socket to remove the defective upstream NOx sensor from the exhaust pipe.

5. 5

   Replace

   Install a new, updated, and compatible upstream NOx sensor.

6. 6

   Reconnect

   Reconnect the wiring harness securely.

7. 7

   Clear and Test

   Clear the fault codes via the diagnostic interface and perform a cold start to verify the heater plausibility error does not return.