Case IH 19023 (DTC 4EDE) - ECU – Engine Control Unit (ECU): NH3 sensor controller failure

The NH3 (Ammonia) sensor monitors the exhaust gas downstream of the SCR catalyst to detect ammonia slip. A controller failure indicates that the sensor's integrated control module has suffered an internal hardware/circuitry failure or has lost its ability to process and transmit data.

• MAXXUM T4E
• 240 Series Axial-Flow Combines
• Magnum
• Maxxum
• Vestrum
• Optum
• N-Series Loader Backhoes
• Farmlift Telehandlers

1. 1

   Check for companion CAN communication codes (e.g., DTC 19024/92EE) or power supply codes (e.g., 19018) which may indicate a wiring issue rather than a failed sensor.

2. 2

   Inspect the wiring harness and connector leading to the NH3 sensor module for chafing, melted wires from exhaust heat, or corrosion inside the connector pins.

3. 3

   Verify that the sensor controller is receiving proper operating voltage and a solid ground from the ECU.

4. 4

   Inspect the exhaust pipe and SCR catalyst near the sensor bung for severe exhaust leaks or physical impact damage.

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the battery to prevent electrical shorts and CAN bus spikes.

2. 2

   Locate the Sensor

   Locate the NH3 sensor, which is mounted on the exhaust tailpipe downstream of the SCR catalyst.

3. 3

   Disconnect

   Unplug the electrical connector from the NH3 sensor controller module.

4. 4

   Removal

   Carefully unscrew the NH3 sensor probe from the exhaust pipe bung. (If the sensor is seized due to heat cycles, penetrating oil may be required).

5. 5

   Installation

   Apply a high-temperature anti-seize compound to the threads of the new sensor (if not already pre-applied by the factory). Thread the new sensor into the exhaust bung and tighten to OEM torque specifications.

6. 6

   Reconnect

   Plug the electrical harness back into the new NH3 sensor controller.

7. 7

   Clear Codes and Reset

   Reconnect the battery. Connect the Case IH Electronic Service Tool (EST) or a compatible diagnostic scanner to clear the inactive fault codes.

8. 8

   Startup Counter Reset

   If the machine was forced into a torque/RPM reduction mode (derate) due to the emissions failure, you must perform a "Startup counter reset" via the diagnostic tool to restore full engine power.