What causes GM code 90?

Failed TCC solenoid Worn TCC clutch or valve body fault Open or shorted TCC wiring Faulty brake switch input keeping TCC off

How do I fix GM code 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

90 Torque Converter Clutch Circuit Error

Q: What does GM code 90 mean?

GM code 90 — Torque Converter Clutch Circuit Error. Applies to 1988-1995 C/K trucks, Camaro, Caprice, Corvette.

Make: GM (1982-1995)
Category: Powertrain - Transmission
Severity: Check Engine Light
Applies to: 1988-1995 C/K trucks, Camaro, Caprice, Corvette

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.

What does GM code 90 mean?

90 — Torque Converter Clutch Circuit Error. This code sets when your vehicle computer detects 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