Case IH 19509 – Engine Control Module (ECM) or Vehicle Control Module (VCM): Status byte error, upstream Sensor Temperature Not okay

This code indicates a failure in the temperature measurement or communication (status byte) of the Upstream NOx Sensor. The engine control system is receiving an invalid or out-of-range temperature signal from this sensor module.

• Tier 4b
• Case IH agricultural equipment
• Case Construction equipment
• N-Series Tractor Loader Backhoes
• FPT Tier 4 Final engines
• F5BFL413 series

1. 1

   Inspect the wiring harness and the electrical connector (e.g., connector C186) going to the upstream NOx sensor module for chafing, melted wires, or corrosion.

2. 2

   Verify that the NOx sensor module is receiving proper battery voltage and has a solid ground connection.

3. 3

   Check the CAN bus communication lines at the sensor connector to ensure the module is communicating properly with the ECM/VCM.

4. 4

   Inspect the exhaust piping between the turbocharger and the DOC/SCR for any leaks that could introduce cold air and skew the sensor's temperature readings.

1. 1

   Turn off machine and disconnect battery

   Turn off the machine, remove the key, and disconnect the battery to prevent electrical spikes.

2. 2

   Locate upstream NOx sensor

   Locate the upstream NOx sensor in the exhaust pipe, situated before the DOC/SCR assembly.

3. 3

   Disconnect electrical harness

   Disconnect the electrical harness connector from the NOx sensor control module.

4. 4

   Unbolt sensor module box

   Unbolt the sensor module box from its mounting bracket on the frame.

5. 5

   Unscrew sensor probe

   Using a specialized NOx sensor socket (typically 22mm or 24mm), carefully unscrew the sensor probe from the exhaust pipe. (If seized, apply penetrating oil and allow it to soak).

6. 6

   Apply anti-seize to new sensor

   Apply a small amount of high-temperature anti-seize to the threads of the new sensor (if not already pre-applied by the manufacturer), being extremely careful not to get any on the sensor tip.

7. 7

   Install new sensor

   Thread the new sensor into the exhaust pipe and torque to OEM specifications (usually around 50 Nm / 37 lb-ft).

8. 8

   Mount sensor module and reconnect harness

   Mount the new sensor module to the bracket and reconnect the electrical harness.

9. 9

   Reconnect battery

   Reconnect the battery.

10. 10

    Clear fault code and verify

    Connect a diagnostic tool (such as the Case Electronic Service Tool - EST) to clear fault code 19509. Start the engine and allow it to reach operating temperature to verify the code does not return.