Deutz-Fahr 139 – ECU: NOx Sensor CAN Reception Timeout

The engine control unit (ECU) has not received the expected data message from the downstream NOx sensor (located after the SCR and DPF systems) within a predefined time. This indicates a communication failure on the CAN bus network between the NOx sensor's integrated control module and the main engine ECU, preventing the engine management system from monitoring the effectiveness of the exhaust aftertreatment system.

• TCD 4.1 L4
• TCD 2013
• TCD 2015
• TCD 2.9 L4
• TCD 3.6 L4

1. 1

   Visually inspect the wiring harness and connectors for the downstream NOx sensor for signs of corrosion, chafing, melted insulation, or bent/loose pins.

2. 2

   With the ignition on, verify that the NOx sensor's control module is receiving the correct voltage and has a solid ground connection at the harness connector.

3. 3

   Perform a CAN bus resistance check with the battery disconnected. Measure resistance between CAN_H and CAN_L (should be approximately 60 Ohms). A reading of ~120 Ohms indicates a missing termination resistor or break; significantly less than 60 Ohms suggests a short circuit.

4. 4

   Perform a CAN bus voltage check with the power on. CAN_H should be between 2.5 and 3.0 V, and CAN_L should be between 2.0 and 2.5 V.

5. 5

   Use a diagnostic tool (such as Deutz SerDia) to read all active and inactive fault codes. Look for other CAN communication codes (U-codes) to determine if there is a broader network issue rather than an isolated sensor problem.

1. 1

   Acquire correct replacement part

   Ensure the replacement NOx sensor has the exact same part number as the original. Sensors from different manufacturers or applications are not cross-compatible.

2. 2

   Prepare for removal

   Allow the exhaust system to cool completely to prevent severe burns and damage to new components.

3. 3

   Remove the old sensor

   Disconnect the electrical connector, unclip the wiring harness, and unbolt the control module. Use a 22mm NOx sensor socket to remove the sensor probe from the exhaust bung. Apply penetrating oil if seized.

4. 4

   Install the new sensor

   Clean the exhaust bung threads. Apply anti-seize to the new sensor threads (avoiding the tip), thread by hand, and torque to OEM specification. Mount the control module, connect the plug, and route the harness securely away from hot components.

5. 5

   Perform post-replacement relearn

   Reconnect the battery and use a diagnostic tool to clear all fault codes. Perform a 'NOx Sensor Replacement' relearn procedure so the ECU recognizes the new sensor. Start the engine and perform a test drive or stationary regeneration to verify the repair.