GM 37 TCC Brake Switch Circuit Error
How to read it
Code 37 reads as 3 flashes, pause, 7 flashes on the check-engine light. Jump terminals A and B on the ALDL connector with the key off, then turn the key on with the engine off and count the check-engine flashes.
New to flash codes? The How to Read GM OBD-I Codes with a Paperclip walks through the test and what the numbers mean. The general OBD-I guide covers the rest.
What does GM code 37 mean?
TCC Brake Switch Circuit Error
Common causes of 37
- Failed or misadjusted brake pedal switch
- Open wiring between the brake switch and ECM
- Blown brake light fuse cutting the signal feed
- Corroded connector at the brake switch
How to fix 37
- Confirm the brake lights work since they share the switch feed
- Check switch adjustment at the brake pedal
- Test for battery voltage in and out of the switch with the pedal pressed
- Inspect wiring to the ECM for opens
- Clear the code and verify TCC unlocks during braking on a road test
Source
Qualified source review
Sources and review
Review: qualified. Read the source limits below.
- GM and Chevrolet OBD1 Trouble Codes (ALDL Fault Code List)
live reference page (troublecodes.net)
Supports: code identity and GM meaning
Fetched directly. Single publisher, so the record is qualified, not verified. Causes and check order are curator-written from the circuit the code names.
https://www.troublecodes.net/gm/
Last updated 2026-09-19.
Report a correction for 37. Include your vehicle, the issue and a source if you have one.