Case IH 19023 – Engine Control Module (ECM): NH3 sensor controller failure

The NH3 (Ammonia) sensor is a critical component of the Selective Catalytic Reduction (SCR) exhaust emissions system. This code indicates that the electronic control unit/controller integrated with or dedicated to the NH3 sensor has suffered an internal failure or is failing to process and transmit data correctly.

• Tier 4b
• 240 Series Axial-Flow Combines
• Maxxum series
• Farmall series
• T7 Series
• Case 580N Backhoe Loaders

1. 1

   Check for related CAN bus codes (specifically 19024 or 19025). If a timeout code is present, the issue might be the wiring rather than the sensor itself.

2. 2

   Inspect the SCR wire harness (e.g., harness 55.988.140) connecting the NH3 sensor controller to the ECM. Look for chafing, melted wires near the exhaust, or corrosion in the connector pins.

3. 3

   Verify that the NH3 sensor controller is receiving proper voltage and has a solid ground connection.

4. 4

   Inspect the exhaust pipe and SCR catalyst area for physical damage, severe soot buildup, or DEF fluid crystallization that could impact the sensor's environment.

1. 1

   Preparation

   Turn off the engine, remove the key, and allow the exhaust/SCR system to cool completely, as the NH3 sensor is mounted directly to the hot exhaust system. Disconnect the machine's battery.

2. 2

   Locate the Sensor

   Locate the NH3 sensor and its attached controller module on the SCR exhaust system (downstream of the DEF injection point).

3. 3

   Disconnect Wiring

   Carefully unplug the electrical connector from the NH3 sensor's electronic control unit.

4. 4

   Removal

   Use the appropriate sensor socket or wrench to unthread the NH3 sensor from the exhaust pipe.

5. 5

   Installation

   Thread the new NH3 sensor assembly into the exhaust bung. Tighten to the OEM torque specification (do not overtighten, as this can damage the sensor element).

6. 6

   Reconnection

   Reconnect the wiring harness to the new sensor controller and reconnect the battery.

7. 7

   Software Reset

   Connect the Case IH Electronic Service Tool (EST). Clear the 19023 fault code and perform any required SCR system resets or sensor initialization procedures so the ECM recognizes the new controller.