Case IH 19007 – Engine ECU / SCR System ECU: NH3 sensor open or short in measuring cell circuit

This fault code indicates an electrical failure within the Selective Catalytic Reduction (SCR) system. Specifically, the system has detected an open circuit or a short circuit in the internal measurement cells of the NH3 (Ammonia) sensor.

• Tier 4b
• 240 Series Axial-Flow Combines (7240, 8240, 9240)
• Magnum
• Steiger
• Maxxum
• Farmall

1. 1

   Inspect the wiring harness leading to the NH3 sensor (located downstream of the SCR catalyst) for melted wires, chafing, or physical damage.

2. 2

   Disconnect the NH3 sensor and inspect the pins on both the sensor side and the harness side for corrosion, pushed-back pins, or moisture intrusion.

3. 3

   Use a multimeter to check the harness for continuity back to the ECU. Test for an open circuit, a short to ground, or a short to voltage on the measuring cell input lines.

4. 4

   If the wiring harness and connectors test perfectly, verify that the fault is an internal short or open within the NH3 sensor's measuring cell itself.

1. 1

   Cool Down

   Park the machine on a level surface, turn off the engine, and allow the exhaust system to cool completely. The NH3 sensor is mounted directly in the exhaust pipe and gets extremely hot.

2. 2

   Disconnect

   Locate the NH3 sensor downstream of the SCR catalyst. Disconnect the electrical connector linking the sensor to the machine's wiring harness.

3. 3

   Removal

   Carefully unscrew the faulty NH3 sensor from the exhaust pipe bung.

4. 4

   Preparation

   Inspect the exhaust bung threads for damage or heavy soot buildup and clean if necessary. If the new sensor does not come with anti-seize pre-applied to the threads, apply a small amount of high-temperature, sensor-safe anti-seize (do not get any on the sensor tip).

5. 5

   Installation

   Thread the new NH3 sensor into the exhaust pipe by hand to prevent cross-threading, then tighten it to the OEM torque specification.

6. 6

   Reconnect

   Plug the electrical connector back into the wiring harness, ensuring the locking tab clicks into place.

7. 7

   Clear Codes

   Turn the key on and use a Case IH diagnostic tool (EST) to clear the inactive 19007 fault code. Start the engine and allow it to reach operating temperature to verify the code does not return.