What does B0337 mean on a Chevy?

B0337. Defrost control switch circuit is open. 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 B0337 on a Chevy?

Open defrost position contacts in the HVAC control head Broken defrost switch signal wire to the HVAC module Corroded or loose HVAC control head connector Failed HVAC control head Chafed defrost switch harness at the control head

How do I fix B0337 on a Chevy?

Confirm the code with a scan tool Inspect and reseat the HVAC control head connector Test the defrost switch signal circuit for an open Repair the open before replacing any parts Replace the HVAC control head only after circuit tests pass, then clear the code and retest

Code

B0337

Defrost control switch circuit is open

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

B0337. Defrost control switch circuit is open. 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

Open defrost position contacts in the HVAC control head
Broken defrost switch signal wire to the HVAC module
Corroded or loose HVAC control head connector
Failed HVAC control head
Chafed defrost switch harness at the control head

Standard procedure

Confirm the code with a scan tool
Inspect and reseat the HVAC control head connector
Test the defrost switch signal circuit for an open
Repair the open before replacing any parts
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 B0337 definition | OBDII.pro
live manufacturer definition (obdii.pro)
Supports: GM manufacturer meaning for B0337
Fetched directly. The GM entry is the brand-family meaning used here. This site is independent of engine-codes and autocodes.
B0337 CHEVROLET Inside Temperature Sensor Short To Ground | Engine-Codes.com
archived reference page (engine-codes.com via Wayback Machine)
Supports: Chevrolet meaning and possible causes for B0337
Fetched directly. Model and year fitment remain curator claims.
B0337 CHEVROLET Inside Temperature Sensor Short To Ground | AutoCodes.com
archived reference page (autocodes.com via Wayback Machine)
Supports: corroboration of Chevrolet meaning and causes for B0337
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 inside temperature sensor short to ground. The circuits differ, so the record uses the GM wording and flags the conflict

Last updated 2026-10-10.

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