Case IH F-4380-12 - ECU – Engine Control Unit (ECU) / Engine Diesel Control (EDC): NH3 sensor open or short in trim resistor circuit

The system has detected an internal short circuit or an open load error on the trim resistor line of the Ammonia (NH3) sensor.

• MAGNUM AFS Connect
• 240 Series Axial-Flow Combines (7240, 8240, 9240)
• N-Series Tractor Loader Backhoes (TLBs)

1. 1

   Wait for the SCR catalyst and exhaust components to cool completely before working on them to avoid severe burns.

2. 2

   Check the NH3 sensor wiring between the sensor controller and the sensor for any physical defects, chafing, or disconnected lines.

3. 3

   Disconnect the slide-lock connector separating the NH3 sensor probe and the sensor module.

4. 4

   Use a digital multimeter to measure the trim resistance of the NH3 sensor probe. The trim resistance must measure between 500 and 2000 ohms. If it falls outside this range, or shows an open/short circuit, the probe is defective.

1. 1

   Disconnect battery

   Disconnect the negative (-) battery cable first to prevent arcing, ensuring the battery compartment is ventilated.

2. 2

   Locate NH3 sensor

   Locate the aftertreatment NH3 sensor. The sensor probe is typically located in the middle of the aftertreatment SCR catalyst, while the sensor module is located on the sensor table on the SCR catalyst.

3. 3

   Remove defective probe

   If the trim resistor circuit failed the diagnostic test, disconnect the slide-lock connector and remove the malfunctioning NH3 sensor probe from the exhaust piping.

4. 4

   Install new probe

   Install the replacement NH3 sensor probe into the SCR catalyst.

5. 5

   Reconnect sensor module

   Reconnect the slide-lock connector to the NH3 sensor module.

6. 6

   Reconnect battery

   Reattach the negative (-) battery cable.

7. 7

   Verify repair

   Use a diagnostic tool to clear the fault codes and run the engine to verify the repair.