GM 90 Torque Converter Clutch Circuit Error
How to read it
Code 90 reads as 9 flashes, pause, 0 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 90 mean?
Torque Converter Clutch Circuit Error
Common causes of 90
- Failed TCC solenoid
- Worn TCC clutch or valve body fault
- Open or shorted TCC wiring
- Faulty brake switch input keeping TCC off
How to fix 90
- Read codes with a paperclip jumper
- Road test and feel for missing TCC lockup at cruise
- Check brake light switch adjustment
- Test TCC solenoid resistance through the trans connector
- Inspect internal wiring if the solenoid tests bad
- Repair and verify lockup engages on the highway
Source
Qualified source review
Sources and review
Review: qualified. Read the source limits below.
- GM OBD1 trouble codes, model and year page
live reference page (troublecodes.net)
Supports: code identity and GM meaning
Fetched directly from the linked model page. Single publisher, so the record is qualified, not verified.
https://www.troublecodes.net/GM/90_453/
Last updated 2026-09-19.
Report a correction for 90. Include your vehicle, the issue and a source if you have one.