Case IH 19018 – Engine Control Unit (ECU): NH3 sensor power supply failure

The system has detected a loss of electrical power or an open/short circuit in the power supply line feeding the Ammonia (NH3) sensor.

• Tier 4b
• 240 Series Axial-Flow Combines
• Maxxum 115
• Maxxum 130
• Farmall 110U
• T7 Series
• Case CE 580N Backhoe Loaders

1. 1

   Inspect the SCR/Exhaust system wire harness leading to the NH3 sensor for physical damage, melted wires, or an open load condition

2. 2

   Disconnect the NH3 sensor and use a multimeter to verify that the sensor is receiving the correct supply voltage from the Engine ECU

3. 3

   Verify that the power supply line is not shorted to ground or shorted to the battery voltage

1. 1

   Power Down

   Turn off the machine and allow the exhaust/SCR system to cool completely, as the NH3 sensor is mounted directly in the exhaust stream.

2. 2

   Locate the Sensor

   Locate the NH3 sensor on the SCR catalyst exhaust pipe.

3. 3

   Resolve Wiring Issues

   If your diagnostic checks revealed a broken wire or blown fuse in the power supply circuit, repair the wire harness (Part of the Selective Catalytic Reduction Wire Harness).

4. 4

   Disconnect Sensor

   If the harness provides proper voltage but the sensor has failed internally, disconnect the sensor's electronic control unit pigtail.

5. 5

   Remove and Install

   Unscrew the faulty NH3 sensor from the exhaust system and thread in the replacement part.

6. 6

   Clear Codes

   Reconnect the harness, turn the key on, and use a diagnostic tool to clear the 19018 / 4DDE code. Run the engine to ensure the DEF/AdBlue warning lights extinguish.