Case IH 19015 – Engine Control Unit (ECU): NH3 sensor heater control failure

The NH3 (Ammonia) sensor relies on an internal heater to reach operating temperature. This fault code triggers when the system detects a malfunction, open circuit, or failure in the heater's control circuit.

• Tier 4b
• 240 Series Axial-Flow Combines
• Farmall Series (90C, 110A, 110U, 130A)
• Maxxum Series
• Maxxum 115
• WD2505 High Speed Windrowers
• 580N Backhoe Loaders
• 821F Wheel Loaders
• 921F Wheel Loaders

1. 1

   Inspect the wiring harness and connectors between the NH3 sensor, its dedicated control unit, and the main engine harness for chafing, heat damage, corrosion, or loose pins.

2. 2

   Verify the power supply and ground circuits to the NH3 sensor controller. Check for related fault codes (e.g., DTC 19018 or DTC 19023) which might indicate a broader electrical issue rather than just the heater.

3. 3

   Inspect the exhaust system and SCR muffler for physical damage or exhaust leaks near the sensor bung.

1. 1

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

2. 2

   Allow the exhaust system and SCR muffler to cool completely.

3. 3

   Locate the NH3 sensor, which is mounted downstream of the SCR muffler / Clean Up Catalyst (CUC).

4. 4

   If necessary for access, remove the SCR muffler and catalyst upper heat shield.

5. 5

   Disconnect the electrical connector linking the NH3 sensor control unit to the main engine wiring harness.

6. 6

   Carefully unscrew and remove the Ammonia (NH3) sensor from the exhaust pipe.

7. 7

   Apply high-temperature anti-seize to the threads of the new sensor (if not pre-applied) and install it into the exhaust bung. Tighten to the manufacturer's specified torque.

8. 8

   Mount the new NH3 sensor control unit and connect the wiring harness.

9. 9

   Reinstall any heat shields or clamps that were removed.

10. 10

    Reconnect the battery, turn on the machine, and use a diagnostic tool to clear the fault codes.