Case IH F-4380-04 - ECU – Engine Control Unit (ECU / EDC) or Aftertreatment Control Module (ACM): NH3 sensor open or short in ground circuit

The control module has detected that the voltage on the ground circuit of the Ammonia (NH3) sensor is below normal or shorted to a low source.

• MAGNUM AFS Connect
• Axial-Flow 140 Series
• Axial-Flow 240 Series
• 7240
• 8240
• 9240
• Magnum
• Steiger
• Optum
• Puma
• Maxxum

1. 1

   Allow the aftertreatment system to cool completely before performing diagnostics to prevent burns.

2. 2

   Inspect the wiring harness and connectors between the NH3 sensor and the ECU/ACM for damaged or pinched wires, corroded terminals, loose/bent pins, or a broken connector housing.

3. 3

   Check the ground circuit of the NH3 sensor for continuity to the ECU/ACM and verify it is not shorted to the chassis ground.

4. 4

   Disconnect the slide-lock connector, remove the NH3 sensor probe from the module, and use a multimeter to measure the trim resistance of the probe (must be between 500 and 2000 ohms).

1. 1

   Disconnect Power

   Disconnect the negative (-) battery cable first to prevent arcing.

2. 2

   Disconnect the Sensor

   Locate the NH3 sensor module and probe on the SCR catalyst. Disconnect the slide-lock electrical connector.

3. 3

   Remove the Faulty Component

   If the wiring harness is the issue, repair the damaged section or install an OEM breakout/repair harness. If the sensor probe failed the resistance test, unscrew the NH3 sensor probe from the exhaust stream. If the module is faulty, unbolt it from the sensor table.

4. 4

   Install the New Part

   Thread the new NH3 sensor probe into the SCR catalyst and tighten to OEM torque specifications.

5. 5

   Reconnect

   Reconnect the slide-lock connector between the probe and the module, then reconnect the main harness. Reattach the negative battery cable.

6. 6

   Clear Codes and Calibrate

   Connect a diagnostic tool (such as the Case IH Electronic Service Tool (EST) or Jaltest) to clear the inactive F-4380-04 fault code. Run an engine aftertreatment system test to verify the sensor is reading correctly and the code does not return.