Case IH F-4377-12 - ECU – Engine ECU: NH3 sensor controller failure

Data from the exhaust aftertreatment NH3 (Ammonia) sensor is erratic, intermittent, or incorrect. This condition points to a defective CAN controller within the NH3 sensor, a disconnected or broken communication cable, an undervoltage condition, or a short circuit in the wiring harness.

• MAGNUM AFS Connect
• Farmall 110A
• Farmall 120A
• Farmall 120C
• Farmall 130A
• Farmall 140A
• Puma
• Magnum
• Steiger
• Quadtrac
• Steiger 620
• Quadtrac 620
• 240 Series Axial-Flow Combines
• 7240 Combine
• 8240 Combine
• 9240 Combine

1. 1

   Verify the presence and correct connection of the NH3 sensor to the CAN network and check the voltage supply to the sensor's CAN controller to ensure it is receiving proper power.

2. 2

   Inspect the wiring harness connecting the sensor to the ECU for short circuits, broken wires, or disconnected plugs. Caution: Do not push multimeter probes directly into the ECU connector; measure from the component side instead.

3. 3

   Check the resistance across the heating element pins on the sensor connector (heater circuit resistance test). If there is no resistance (open circuit), the sensor is definitively bad.

1. 1

   Locate the NH3 sensor

   Locate the NH3 sensor on the exhaust aftertreatment system (SCR muffler/catalyst area).

2. 2

   Remove heat shield

   Depending on the machine's clearance, you may need to remove the SCR muffler and catalyst upper heat shield for access.

3. 3

   Remove temperature sensor

   If obstructed, temporarily remove the SCR catalyst downstream temperature sensor.

4. 4

   Disconnect electrical harness

   Disconnect the electrical harness from the defective Ammonia (NH3) sensor.

5. 5

   Remove NH3 sensor

   Unthread and remove the NH3 sensor from the exhaust outlet pipe.

6. 6

   Install new NH3 sensor

   Install the new NH3 sensor into the exhaust pipe and tighten to OEM specifications.

7. 7

   Reconnect electrical harness

   Reconnect the electrical harness.

8. 8

   Reinstall components

   Reinstall any heat shields or temperature sensors that were removed during disassembly.

9. 9

   Clear fault codes

   Clear the fault codes from the Engine ECU and verify normal operation.