What does U029D Lost Communication With NOX Sensor A mean?
The U029D code stands for "Lost Communication With NOX Sensor A".
This is a generic diagnostic trouble code that applies to most OBD-II vehicle makes and models.
It means that the NOX Sensor A (NOXS-A) and other control modules on the vehicle are not communicating with each other.
The NOX Sensor A is typically located screwed into the exhaust pipe behind the SCR catalytic converter.
It receives inputs from various sensors and communicates with the sensor to verify if the catalyst is controlling NOx.
Without proper communication between the modules, control modules cannot exchange information, and your scan tool may or may not be able to get information from the vehicle.
This code can cause the Malfunction Indicator Light to illuminate and may result in the NOXS-A being inoperative or not producing any voltage.
The causes for this code can include an open circuit in the CAN bus, a short to power or ground in the CAN bus circuit, no power or ground to the NOXS-A module, or a faulty control module.
Troubleshooting steps may vary depending on the manufacturer and the type of communication system used in the vehicle.
It is recommended to check for any technical service bulletins for your specific vehicle and to diagnose any other related codes before diagnosing the U029D code.
If the basic codes have been thoroughly diagnosed and repaired and the U029D code persists, further diagnostics and repairs may be required, possibly including seeking assistance from a trained automotive diagnostician.
U029D Symptoms
- Malfunction Indicator Light ON
- NOXS-A wonu0027t power up / inoperative / no voltage produced by sensor module
Possible U029D Causes
- Open in the CAN bus + or - circuit
- Short to power or ground in either CAN bus circuit
- No power or ground to NOXS-A module
- Rarely - faulty control module
Troubleshooting U029D error code
- Check for technical service bulletins (TSB) for your vehicle
- Diagnose other diagnostic fault codes related to bus communication or battery / ignition
- Access the NOXS-A and clear the diagnostic trouble codes
- Check all fuses that power up the NOXS-A module
- Check all grounds for the NOXS-A
- Clean the grounds if necessary
- Inspect the connectors and wiring for any damage
- Clean the terminals inside the connectors if necessary
- Perform voltage checks at the NOXS-A for power and grounds
- Check the communication circuits (CAN C+ and CAN C-)
- Seek assistance from a trained automotive diagnostician if all tests pass and communication is still not possible or the fault code cannot be cleared
- Consider the possibility of a failed NOXS-A module
