Case IH 19016 (DTC 37EE) - ECU – Engine Control Unit (ECU / EDC): NH3 sensor heater performance failure

The NH3 (Ammonia) sensor is a "smart sensor" located in the exhaust system that contains an internal heating element. Once the exhaust system reaches the dew point, the sensor is commanded to heat up to its operating temperature within a specific timeframe. If the sensor fails to reach this heated state in the allotted time, the system detects that the sensor heating is defective or insufficient, triggering this fault code.

• MAXXUM T4E
• 240 Series Axial-Flow Combines (7240, 8240, 9240)
• Maxxum 115
• Farmall 110U
• 580N Backhoe Loaders
• 521G Wheel Loaders
• N Series Loaders

1. 1

   Inspect the NH3 sensor, its integrated controller, and the wiring harness for physical damage, melted wires, or corrosion.

2. 2

   Check the wiring between the NH3 sensor controller and the Engine ECU for open circuits, short circuits, or disconnected pins.

3. 3

   Verify the power supply and ground to the sensor. Check for excessive voltage drop (+/- 1V) and verify current consumption (max 0.5A) on the sensor lines.

4. 4

   If the visual inspection and wiring checks are OK, the fault confirms that the sensor's internal heater is defective and the sensor must be replaced.

1. 1

   Preparation

   Turn off the engine, remove the key, and allow the exhaust system to cool completely, as the NH3 sensor is located in the high-temperature SCR exhaust stream.

2. 2

   Disconnect Power

   Disconnect the machine's battery to prevent electrical shorts during the repair.

3. 3

   Locate the Sensor

   Locate the NH3 sensor on the exhaust aftertreatment system (typically downstream of the SCR catalyst).

4. 4

   Disconnect Wiring

   Unplug the electrical connector from the NH3 sensor harness.

5. 5

   Remove the Sensor

   Using the appropriate sensor socket or wrench, carefully unscrew and remove the defective NH3 sensor from the exhaust pipe.

6. 6

   Install the New Sensor

   Apply a high-temperature anti-seize compound to the threads of the new sensor (if not pre-applied by the manufacturer), ensuring no compound touches the sensor tip. Thread it into the exhaust pipe and torque to OEM specifications.

7. 7

   Reconnect

   Plug the electrical connector back into the machine's harness.

8. 8

   Clear Codes

   Reconnect the battery, turn on the machine, and use a diagnostic service tool (such as the Case IH EST) to clear the inactive fault codes. Run the engine to operating temperature to verify the sensor reaches its heated state and the code does not return.