Deutz-Fahr 135 – ECM: Pre-Cat NOx Sensor Calibration Failure

The Engine Control Module (ECM) has determined that the pre-catalyst NOx sensor is not providing a valid signal during its internal calibration process (specifically Calibration Message 2). This indicates a problem with the communication or functionality of the sensor. Because NOx sensors perform self-calibration and cannot be calibrated in the field, an out-of-calibration status typically means the sensor has suffered an internal malfunction and must be replaced.

• TCD 3.6
• TCD 4.1

1. 1

   Read all active and inactive fault codes using a diagnostic tool (e.g., Deutz SerDia) to rule out related aftertreatment, wiring, or power supply issues.

2. 2

   Visually inspect the pre-cat NOx sensor wiring harness and connectors for chafing, melting from hot exhaust components, corrosion, or loose pins.

3. 3

   Check the power supply at the sensor's harness-side connector with the ignition on (engine off); voltage should be above 11.5 volts.

4. 4

   Measure CAN bus resistance at the sensor connector (should be between 50 and 70 ohms) to verify communication line integrity.

5. 5

   Inspect the exhaust system upstream of the NOx sensor for leaks that could introduce oxygen and skew the sensor readings.

1. 1

   Locate the Sensor

   The pre-cat (or upstream) NOx sensor is located in the exhaust system between the turbocharger and the SCR catalyst.

2. 2

   Allow the Exhaust to Cool

   Ensure the exhaust system is completely cool before attempting to remove the sensor to prevent burns.

3. 3

   Remove the Old Sensor

   Disconnect the electrical connector. Carefully unscrew the NOx sensor probe from the exhaust pipe. These can be seized, so use appropriate tools and penetrating oil if necessary. The sensor and its integrated control module must be replaced as a single unit.

4. 4

   Prepare for Installation

   Clean the threads in the exhaust port using a thread chaser (e.g., M20 x 1.5 for many sensors) to ensure a clean installation and proper sealing.

5. 5

   Install the New Sensor

   Apply a small amount of ceramic anti-seize compound to the new sensor's threads, being careful not to get any on the sensor tip. Thread the new sensor in by hand and then torque it to the manufacturer's specification (typically 40-60 Nm).

6. 6

   Connect and Secure

   Securely attach the new sensor's electrical connector. Route the wiring harness correctly, ensuring it is secured in its designated clips and is not touching any hot surfaces.

7. 7

   Clear Codes and Perform Relearn/Calibration

   Use a diagnostic tool to clear the P1364 / SPN 3216 FMI 13 fault code from the ECM. After clearing the codes, a 'relearn' or 'reset' procedure is often required. This may involve a specific function in the diagnostic tool or a defined drive cycle (e.g., driving at highway speeds for a set duration) to allow the ECM to recognize and adapt to the new sensor.