Deutz-Fahr 141 – EMR4: Calibration Message 1 from the Post-Cat NOx Sensor Has Failed

The Engine Control Module (EMR4) did not receive a valid calibration or status message from the downstream (post-catalyst) NOx sensor during a critical phase such as startup or self-test. This is a CAN-bus communication timeout error (AT1OGCVol2) responsible for transmitting sensor calibration and factor data, indicating that the communication link or the sensor's ability to transmit its health status has been compromised.

• TCD 3.6
• TCD2013L06 4V

1. 1

   Verify that fault code 141 (SPN 523942 / FMI 9) is active and note any other active fault codes related to the aftertreatment system, CAN bus, or power supply.

2. 2

   Visually inspect the post-catalyst NOx sensor, wiring harness, and connector for signs of corrosion, moisture ingress, damaged/melted wiring, or physical damage to the sensor body or the control module.

3. 3

   Inspect the sensor head for heavy contamination of soot or crystallized AdBlue/DEF residue, which can indicate other system faults like over-dosing or poor combustion.

4. 4

   Using a multimeter and wiring diagram, verify the NOx sensor is receiving the correct voltage and has a solid ground connection at the harness connector.

5. 5

   Check the integrity of the CAN bus communication wiring to the sensor.

6. 6

   Monitor live data from the post-catalyst NOx sensor using a diagnostic tool; frozen, erratic, or zero readings strongly suggest a failed sensor.

1. 1

   Address underlying issues

   If diagnostic checks revealed excessive soot or AdBlue residue on the old sensor, investigate and repair the root cause (e.g., faulty injectors, DPF issues, or AdBlue dosing problems) before replacing the NOx sensor.

2. 2

   Replace NOx sensor

   Allow the exhaust system to cool. Disconnect the wiring harness and remove the old sensor using the correct size wrench. Apply a small amount of anti-seize compound to the threads of the new sensor (avoiding the tip). Install and tighten to the manufacturer's specified torque. Securely connect and route the wiring harness, clipping it into any vehicle-specific fixing points to prevent future damage.

3. 3

   Clear fault codes

   Use a diagnostic tool to clear the fault codes from the ECM after the new sensor is installed.

4. 4

   Perform system relearn

   Perform a system relearn procedure or an extended test drive to allow the ECM to recognize the new sensor. A forced DPF regeneration cycle may be required to validate the repair.