Case IH F-4382-03 - ECU – Engine Control Unit (ECU) or NH3 Electronic Control Unit / Dosing Control Unit (DCU): Exhaust Aftertreatment Ammonia (NH3) Sensor Heater Circuit

The NH3 sensor utilizes an internal heating element to burn off moisture and dew from the sensor tip. When this heating circuit shorts out, the sensor cannot regulate its temperature properly, leading to erratic data, overheating, or total sensor failure.

• MAGNUM AFS Connect
• Puma
• Magnum
• Steiger
• Quadtrac
• Maxxum
• Farmall 110A
• Farmall 120A
• Farmall 130A
• Farmall 140A
• Farmall 110U
• Farmall 120C
• Axial-Flow series
• TV380 Compact Track Loaders
• 580N Backhoes

1. 1

   Inspect the wiring harness and connector leading to the NH3 sensor for melted wires, corrosion, or pinched lines that could cause a short to a high voltage source.

2. 2

   Unplug the NH3 sensor and use a multimeter to check the resistance across the heating element pins on the sensor itself. If there is no resistance (a dead short) or an open circuit, the sensor's internal heater has failed and the sensor must be replaced.

3. 3

   Check the harness side for proper voltage supply from the ECU/DCU to rule out a wiring short in the main harness.

1. 1

   Cool Down

   Ensure the machine is turned off and the exhaust/SCR system has completely cooled. The SCR muffler and catalyst operate at extremely high temperatures.

2. 2

   Locate the Sensor

   Locate the NH3 sensor on the SCR muffler/catalyst assembly. It is typically mounted downstream, near the NOx sensor and SCR outlet temperature sensor.

3. 3

   Disconnect

   Disconnect the electrical harness connector from the NH3 sensor.

4. 4

   Removal

   Carefully unscrew and remove the faulty NH3 sensor from the exhaust pipe/SCR muffler.

5. 5

   Installation

   Apply high-temperature anti-seize to the threads of the new sensor (if not pre-applied by the manufacturer) and install it into the exhaust pipe, tightening to OEM torque specifications.

6. 6

   Reconnect

   Reconnect the electrical harness securely.

7. 7

   Clear Codes

   Use the Case IH Electronic Service Tool (EST) to clear the fault codes and run an aftertreatment system test to verify the new heater circuit is operating correctly.