What does B0333 mean on a Chevy?

B0333. Defrost control switch circuit malfunction. The HVAC module cannot read the defrost selection and the body warning light comes on. Applies to Chevrolet, GMC, Buick, Cadillac, Pontiac, Oldsmobile and Saturn models that use this code.

What causes B0333 on a Chevy?

Worn defrost position contacts in the HVAC control head Defrost switch signal circuit shorted or intermittent Corroded HVAC control head connector terminals Failed HVAC control head Moisture in the defrost switch making contact erratic

How do I fix B0333 on a Chevy?

Confirm the code with a scan tool Inspect and reseat the HVAC control head connector Backprobe the defrost switch signal circuit Monitor defrost switch status on the scan tool while cycling the switch Replace the HVAC control head only after circuit tests pass, then clear the code and retest

Code

B0333

Defrost control switch circuit malfunction

Category: Body
Severity: Body Warning Light
Applies to: Chevrolet, GMC, Buick, Cadillac, Pontiac, Oldsmobile and Saturn models that use this code
Related: No single generic twin. See OBD Codes List

What it means

B0333. Defrost control switch circuit malfunction. The HVAC module cannot read the defrost selection 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

Worn defrost position contacts in the HVAC control head
Defrost switch signal circuit shorted or intermittent
Corroded HVAC control head connector terminals
Failed HVAC control head
Moisture in the defrost switch making contact erratic

Standard procedure

Confirm the code with a scan tool
Inspect and reseat the HVAC control head connector
Backprobe the defrost switch signal circuit
Monitor defrost switch status on the scan tool while cycling the switch
Replace the HVAC control head 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: qualified. Read the source limits below.

Code B0333 definition | OBDII.pro
live manufacturer definition (obdii.pro)
Supports: GM manufacturer meaning for B0333
Fetched directly. The GM entry is the brand-family meaning used here. This site is independent of engine-codes and autocodes.
B0333 CHEVROLET Ambient Air Temperature Sensor Open | Engine-Codes.com
archived reference page (engine-codes.com via Wayback Machine)
Supports: Chevrolet meaning and possible causes for B0333
Fetched directly. Model and year fitment remain curator claims.
B0333 CHEVROLET Ambient Air Temperature Sensor Open | AutoCodes.com
archived reference page (autocodes.com via Wayback Machine)
Supports: corroboration of Chevrolet meaning and causes for B0333
Same Chevrolet text as the engine-codes page (both sites share one publisher).

Review note: obdii.pro GM names the climate control defrost switch circuit; the archived Chevrolet page names the ambient air temperature sensor open. The circuits differ, so the record uses the GM wording and flags the conflict

Last updated 2026-10-10.

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