Case IH 19008 – Engine Control Unit (ECU): NH3 sensor open or short in ground circuit

The engine's control system has detected a lack of electrical continuity (an open circuit) or an improper ground connection (a short) in the wiring circuit dedicated to the Ammonia (NH3) sensor.

• Tier 4b
• 240 Series Axial-Flow Combines
• Farmall 110A
• Farmall 120A
• Farmall 130A
• Farmall 140A
• Farmall 110U (Tier 4B)
• Maxxum 115 (Tier 4B)
• TV380 Compact Track Loaders
• Case 580N Backhoe Loaders
• 821F/921F Wheel Loaders

1. 1

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

2. 2

   Visually inspect the wiring harness connecting the NH3 sensor and its dedicated processor module to the main engine harness. Look for chafing, melting from exhaust heat, or breaks.

3. 3

   Use a multimeter to test the ground pins on the sensor's connector for continuity to the chassis/battery ground.

4. 4

   Disconnect the sensor and check the pins inside the connector. Ensure no pins are bent, corroded, or pushed back into the housing.

1. 1

   Safety First

   Turn off the machine and disconnect the battery. Allow the exhaust system to cool completely, as the SCR muffler operates at extremely high temperatures.

2. 2

   Access the Sensor

   Locate the NH3 sensor downstream of the SCR catalyst. Depending on the machine model, you may need to remove the SCR muffler upper heat shield to gain access.

3. 3

   Disconnect

   Unplug the electrical connector from the NH3 sensor's processor/ECU.

4. 4

   Remove

   Carefully unscrew the NH3 sensor probe from the exhaust pipe.

5. 5

   Install

   Apply a high-temperature anti-seize compound to the threads of the new sensor (if it does not come pre-applied). Thread it into the exhaust pipe and tighten to the OEM torque specification.

6. 6

   Reconnect

   Secure the attached NH3 processor module to its mounting bracket and plug the electrical harness back in.

7. 7

   Reassemble

   Reinstall any heat shields or clamps that were removed during access.

8. 8

   Clear Codes

   Reconnect the battery, turn the key on, and use a diagnostic tool to clear the 19008 fault code. Start the engine and verify the code does not return.