Case IH 19507 – Engine Control Unit (ECU) or Vehicle Control Module (VCM): Upstream NOx Sensor: Lambda signals is invalid

This code indicates that the Upstream Nitrogen Oxide (NOx) sensor is reporting an implausible or invalid Lambda (oxygen) reading. An invalid signal typically means the sensor's internal lambda measurement circuit has failed, the sensor probe is heavily contaminated, or there is a severe exhaust leak skewing the oxygen readings.

• Tier 4b
• tractors
• combines
• sprayers
• Case CE

1. 1

   Inspect the wiring harness and the specific connector (e.g., C186) leading to the upstream NOx sensor. Look for melted wires, chafing, or corrosion in the terminal pins, as communication drops can trigger invalid signal codes.

2. 2

   Inspect the exhaust manifold and the piping between the engine turbocharger and the upstream NOx sensor. An exhaust leak can draw in ambient air, causing the sensor to read an artificially high (and invalid) oxygen/lambda level.

3. 3

   Check for excessive soot from a separate fueling issue (e.g., a leaking injector) that can blind the sensor probe.

4. 4

   Verify the sensor is receiving proper voltage (typically 24V or 12V depending on the machine's architecture) and has a solid ground connection.

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the battery to prevent electrical shorts and ensure the ECU resets.

2. 2

   Locate the Sensor

   Locate the Upstream NOx sensor. It is threaded into the exhaust pipe directly after the turbocharger and before the DOC/SCR aftertreatment assembly.

3. 3

   Disconnect the Module

   Disconnect the main electrical harness from the sensor's control module.

4. 4

   Remove the Sensor

   Unbolt the sensor's control module from its mounting bracket. Using a specialized NOx sensor socket or a 22mm wrench, carefully unscrew the sensor probe from the exhaust pipe. Note: If the sensor is seized due to heat cycling, apply penetrating oil and allow it to soak before applying torque to avoid stripping the exhaust bung threads.

5. 5

   Prepare the New Sensor

   Apply a high-temperature anti-seize compound to the threads of the new NOx sensor (if it does not already come pre-coated from the factory). Do not get anti-seize on the sensor probe tip.

6. 6

   Installation

   Thread the new sensor into the exhaust bung by hand to prevent cross-threading, then torque to OEM specifications (typically 50 ± 10 Nm).

7. 7

   Route Wiring

   Mount the new sensor's control module to the bracket. Route the cable carefully, ensuring it is secured at multiple locations (within 100mm of the module) to prevent damage from exhaust vibration and extreme heat. Reconnect the electrical harness.

8. 8

   Clear Codes and Test

   Reconnect the battery. Connect a diagnostic tool (such as the CNH Electronic Service Tool - EST) to clear the inactive 19507 fault code. Run the engine and perform an aftertreatment system test to verify the sensor is reading Lambda and NOx parameters correctly.