U029D
Lost Communication With NOx Sensor A
The vehicle bus reports loss of communication with NOx sensor A (smart sensor with own ECU). The SCR catalyst control loop loses its actual NOx feedback and may switch to substitute values.
The vehicle bus reports loss of communication with NOx sensor A (smart sensor with own ECU). The SCR catalyst control loop loses its actual NOx feedback and may switch to substitute values.
Common causes
- high
Bus wiring open or shorted
One of the most commonly reported causes for this code — check this first.
Typical part cost: $390-1980
- medium
Module without power or ground
A plausible cause — test and verify before replacing parts.
Typical part cost: $390-1980
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First things to check
- 1Confirm the code with a scan tool and check for additional related codes.
- 2Inspect the relevant sensors, wiring, and connectors for damage or corrosion.
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Related codes
See related trouble codes
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Frequently asked questions
What does U029D mean?
U029D means "Lost Communication With NOx Sensor A". It is a generic OBD-II code that points to a fault in the network / communication.
What are the most common causes of U029D?
bus wiring open or shorted; module without power or ground; module failed — these are the most commonly reported causes. Verify with a proper diagnosis before replacing parts, or use the Wrenchify app for a vehicle-specific diagnosis.
Can I keep driving with this code?
This code can put the vehicle into limp or reduced-power mode. Avoid extended driving and have the vehicle diagnosed promptly. Use the Wrenchify app for a full diagnosis specific to your vehicle.
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