Its in a 87 monte ss. It will only unlock when the trans goes into first. Everything is still computer controlled. AS soon as it shifts into second the tcc locks up.(after it gets up to temp) and it wont unlock untill car is stopped and has gone into first it almost stalls out. I know it should unlock when I hit the brakes but doesnt. have any ideas?

 

sounds like the brake switch just isn't working. Either fix that or take the TCC control away from the computer.
A tranny shop can put in a pressure switch to control lockup at a fairly low price.

 

I agree with the brake light switch possibility.

Might have to replace the lock up conv. solenoid. (no big deal)



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ASE Mechanic/Machinist/Smog Tech

1999 NBM Trans Am
1986 Chevy 3/4 ton pick up
1981 corvette
1995 Kawi ZX6R

GO #3

 

Wouldn't this be a short to ground on the ground side of the solenoid circuit? The solenoid always has 12 vdc to the power side when the ignition switch is on, all the ECM and brake light switch do is provide a path to ground. The way his is acting is what would happen if you hooked up a manual switch to ground and left it closed all the time (no pressure to the solenoid in 1st). That doesn't sound like a brake light switch to me. Perhaps a pinched or chafed wire creating a path to ground.

Or, the solenoid is stuck in the closed position w/o power.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.93 limited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/LB9 block, ZZ3 cam and intake, WP 305 heads ported & polished, Hooker headers & y-pipe, hi-flow cat).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

The ECM interrupts the ground, the brake switch interrupts the +12.

 

Okay. By "interupts the ground", that means that no ground would be provided until the ECM thinks the TCC should be locked up (solenoid engerized by completing the circuit).

But does the brake switch still make sense? If it was "bad", it would not send voltage to the solenoid (which it should be doing unless the brake is slightly applied), whereas the problem seems to be that the solenoid is constantly energized.

Or, do I still have something wrong?

 

That's right, it doesn't make sense to me that it's the brake switch either. In any case, start here: