Case IH 3170 – Engine Control Unit (ECU): NH3 Sensor value not mounted in proper position

Indicates that the NH3 sensor signal is not changing or the NH3 Sensor value not mounted in proper position. The sensor is either physically out of position, covered in moisture/product, or the internal heating circuit has failed, causing the sensor to read a constant value of zero. This triggers an engine derate (inducement) and power loss.

• Puma tractors
• Magnum tractors (e.g., 250-380)
• Steiger / Quadtrac tractors
• 240 Series Axial-Flow Combines
• Patriot Sprayers (e.g., 3240)

1. 1

   Verify that the NH3 sensor is mounted in the correct position in the exhaust system and ensure that product or moisture is not collecting on the sensor tip.

2. 2

   Disconnect the sensor and use a multimeter to check the resistance across the heating element pins on the sensor connector. An open circuit (no resistance) indicates a failed internal heater.

3. 3

   Inspect the wiring harness between the ECU and the NH3 sensor to ensure it is intact and free of shorts or corrosion.

1. 1

   Turn off the machine and allow the exhaust/SCR system to cool completely.

2. 2

   Disconnect the wiring harness from the NH3 sensor.

3. 3

   Remove the faulty NH3 sensor from the exhaust/SCR dosing module piping.

4. 4

   Install the new NH3 sensor into the proper mounting position and reconnect the wiring harness.

5. 5

   Connect the Case IH Electronic Service Tool (EST) and navigate to the configure menu to perform the SCR Fault Repair Verification Test.

   Because this fault causes an emissions inducement (derate), simply replacing the part will not clear the code.

6. 6

   Using the EST, perform the Engine Restart Counter Reset / Unlock Inducement configuration to restore full engine power before returning the machine to service.