Air mix door 1 range fault
What it means
B0409. Air mix door 1 range fault. The driver side temperature door moves outside its expected range 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
- Driver side air mix door binding in its travel
- Stripped gears in the driver side air mix door actuator
- Driver side air mix door position sensor reporting outside range
- Obstruction in the driver side air mix door travel
- Failed driver side air mix door actuator
Standard procedure
- Confirm the code with a scan tool
- Command the driver side air mix door and watch for a full sweep
- Inspect the driver side air mix door for binding or an obstruction
- Test the driver side air mix door position feedback
- Replace the driver side air mix door actuator only after circuit tests pass, then clear the code and retest
Look up another code
Press / to jump to the box. Chevy-enhanced powertrain, body, chassis and network codes.
Sources and review
Review: checked against the recorded source material.
- Code B0409 definition | OBDII.pro
live manufacturer definition (obdii.pro)
Supports: GM manufacturer meaning for B0409
Fetched directly. The GM entry is the brand-family meaning used here. This site is independent of engine-codes and autocodes.
- B0409 CHEVROLET Temperature Control 1 Circuit Range | Engine-Codes.com
archived reference page (engine-codes.com via Wayback Machine)
Supports: Chevrolet meaning and possible causes for B0409
Fetched directly. Model and year fitment remain curator claims.
- B0409 CHEVROLET Temperature Control 1 Circuit Range | AutoCodes.com
archived reference page (autocodes.com via Wayback Machine)
Supports: corroboration of Chevrolet meaning and causes for B0409
Same Chevrolet text as the engine-codes page (both sites share one publisher).
Last updated 2026-10-10.
Report a correction for B0409. Include your vehicle, the issue and a source if you have one.