Auxiliary air temperature actuator range or performance problem
What it means
B0429. Auxiliary air temperature actuator range or performance problem. The rear air mix door cannot hold the commanded position and the body warning light comes on.. This Chevy-enhanced code applies to Chevrolet, GMC, Buick, Cadillac, Pontiac, Oldsmobile and Saturn models that use this code.
Findings, check these first
- Rear auxiliary air temperature actuator slipping under command
- Rear air mix door binding after it moves
- Worn gears in the rear auxiliary air temperature actuator
- Failed position sensor in the rear auxiliary air temperature actuator
- Faulty output in the auxiliary HVAC control module
Standard procedure
- Confirm the code with a scan tool
- Command the rear air mix door and watch it hold the commanded position
- Inspect the rear air mix door for binding
- Test the rear auxiliary actuator position feedback
- Replace the rear auxiliary air temperature actuator only after circuit tests pass, then clear the code and retest
Look up another code
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Sources and review
Review: checked against the recorded source material.
- B0429 CHEVROLET Code: Meaning, Causes, and Symptoms | OBD2 Codes - OBD2 Codes
live reference page (obd2-codes.co)
Supports: CHEVROLET and GM-family meaning and likely causes for B0429
Fetched directly. B0429 reads "Auxiliary Air Temperature Actuator Range/Performance".
- Code B0429 meaning and causes | OBDII.pro
live reference page (obdii.pro)
Supports: independent corroboration of the GM meaning
Fetched directly. obdii.pro is a separate publisher and gives the GM meaning as: Temperature Control #3 Rear Circuit Range/Performance More details about the error B0429 and possible reasons for its occurrence.
Last updated 2026-10-10.
Report a correction for B0429. Include your vehicle, the issue and a source if you have one.