Case IH F-4383-04 - ECU – Dosing Control Unit (DCU) / Engine Control Unit (ECU): Internal short circuit or open load error on the temperature cell input line

The NH3 (Ammonia) sensor relies on an internal heating element and temperature cell to reach operating temperature and accurately measure ammonia slip in the exhaust. This code triggers when the circuit for this temperature cell/heater fails, meaning the sensor can no longer function correctly.

• MAGNUM AFS Connect
• Puma series tractors
• Magnum series tractors
• Steiger / Quadtrac series tractors
• Quadtrac 620
• Axial-Flow Combines
• 240 series
• Backhoe Loaders
• 580N

1. 1

   Inspect the NH3 sensor's 8-pin electrical connector and the surrounding wiring harness for corrosion, melted wires, or loose connections.

2. 2

   Check the resistance across the heating element pins on the sensor connector. If there is no resistance, the sensor has an internal open circuit and is definitively bad.

3. 3

   Verify that the ECU/DCU is supplying the correct voltage to the sensor to rule out a broader harness or module failure.

1. 1

   Disconnect battery

   Turn off the machine and disconnect battery power to prevent electrical shorts.

2. 2

   Locate NH3 sensor

   Locate the NH3 sensor probe, which is mounted in the middle of the aftertreatment SCR catalyst / exhaust pipe.

3. 3

   Disconnect electrical connector

   Disconnect the 8-pin electrical connector from the sensor.

4. 4

   Remove faulty sensor

   Unscrew and remove the faulty NH3 sensor from the exhaust line.

5. 5

   Install new sensor

   Install the new NH3 sensor into the exhaust pipe.

6. 6

   Reconnect harness

   Reconnect the electrical harness.

7. 7

   Clear fault codes

   Reconnect the battery and use a diagnostic tool (such as the Jaltest tool or Case IH Electronic Service Tool) to clear the active/permanent fault codes from the ECU.

8. 8

   Verify ECU module replacement

   Verify if your specific machine requires the updated module alongside the sensor. For certain models (like the Quadtrac 620), OEM parts diagrams state: 'If Sensor Fails, Also Replace With Updated ECU Module'.