Case IH 19508 – Vehicle Control Module (VCM) or Engine Control Unit (ECU): Upstream NOx Sensor: NOx signals invalid

The control module is receiving an implausible, out-of-range, or missing nitrogen oxide (NOx) concentration signal from the sensor located upstream of the Selective Catalytic Reduction (SCR) catalyst.

• Tier 4b
• 580N
• 580SN
• 580SN WT
• 590SN
• Case IH tractors
• Case CE wheel loaders

1. 1

   Inspect the wiring harness and the CAN bus connector leading to the upstream NOx sensor for chafed wires, corrosion, or loose pins.

2. 2

   Check for any exhaust leaks upstream of the NOx sensor.

3. 3

   Verify that there are no other active CAN bus communication faults (e.g., timeout errors).

4. 4

   Inspect the sensor probe and module for severe soot buildup, physical impact damage, or melted wiring.

1. 1

   Preparation

   Ensure the machine is parked on a level surface, the engine is turned off, and the battery disconnect switch is engaged. Allow the exhaust system to cool completely to prevent severe burns.

2. 2

   Locate the Sensor

   Locate the upstream NOx sensor. It is threaded into the exhaust pipe between the engine turbocharger and the Diesel Oxidation Catalyst (DOC) / SCR assembly.

3. 3

   Disconnect

   Unplug the sensor's electrical connector from the main engine wiring harness.

4. 4

   Removal

   Using a specialized NOx sensor socket or a 22mm wrench, carefully unscrew the sensor from the exhaust pipe.

5. 5

   Installation

   Apply a small amount of high-temperature anti-seize compound to the threads of the new sensor (if it is not already pre-applied from the factory). Caution: Do not allow any anti-seize to touch the sensor tip, as this will permanently ruin the sensor.

6. 6

   Torque

   Thread the new sensor into the exhaust pipe by hand to prevent cross-threading, then tighten it to the manufacturer's specified torque (typically around 50 Nm / 37 lb-ft).

7. 7

   Reconnect

   Route the sensor wiring away from extreme heat sources and reconnect the electrical plug until it clicks securely.

8. 8

   Clear Codes

   Reconnect the battery. Use the CNH Electronic Service Tool (EST) or a compatible diagnostic scanner to clear fault code 19508. Run the engine through a standard operating cycle to verify the code does not return.