I'm working on finishing up my current 93Z28 project.

This is the problem, the convertor stays locked up all the time. I unplugged the connector at the trans so i I could drive it, I checked the A terminal and it has power to it when the key is on, I didn't think it was supposed to have power untill the ECM told it to. Is this correct? It has a tune in it from PCMforless. Could the ECM be telling it to stay locked up all the time? Thanks.

Jason

 

Pin A has power all the time through the brake switch. Applying the brakes will turn the power off. The ECM grounds pin D to lock and unlock the TCC.

 

What would keep it locked up constantly? A bad TCC solenoid? I guess I'm not understanding how the TCC system works. I thought the A terminal engergized the TCC and that's what made it lock up.

 

If the solenoid is clogged and isn't allowing fluid to pass through it when un-energized (normal operation), the clutch will stay locked. The circuit is switched with a pressure switch to ground (pressure switch is activated in 3rd/4th gear (depends on the setup) and grounds the TCC solenoid)... The ECM, as Apeiron said, feeds ground to that circuit when deemed necessary...

If unplugging the trans connector fixes the lockup-all-the-time problem, it probably isn't clogged.

 

The 4th gear pressure switch doesn't directly affect the operation of the TCC.

 

Isn't it a part of the ground path for the TCC solenoid (or did they not do it that way on stock setups)?

EDIT: Okay, maybe my thinking was skewed by how to set up a 700R4 for a non-computer controlled application. I do know that fluid is not routed to the TCC fluid circuit in 1st gear (to prevent killing the engine if the solenoid sticks). Then the ECM controlled applications can lock up as early as 2nd gear... okay, yeah, thats how my old '88 bird was set up, you could jumper the ALDL TCC test pin and lock it up in 2nd gear.. Okay, sorry bout the pressure switch stuff, didn't mean to confuse..

 

ok, i am lost now. and the 93 is computer controlled.

 

What are the symptoms that lead you to believe the TCC is staying locked up all the time?

 

you can feel it, it bucks and when you come to a stop sign it will kill the engine because the RPMS drop so low, it's like driving a manual tranny car and not pushing the clutch in when you come to a stop light. when it shifts is horrible because it's locked, it will never unlock unless i pull it down into 1st gear where there is no TCC circut.

 

The TCC operates the same regardless of whether the shifter is in 1st or not.

 

first gear doesn't lock up because it doesn't have the previson for it in the valvebody, that's why it locks up in 2nd, 3rd and 4th, atleast that's the way i understood it when it was explained to me. maybe i kicked it up in neutrul, it's been about 3 weeks since i have driving it with it hooked up.

 

TCC apply pressure comes from the second gear circuit, but it doesn't matter if the shifter is in 1st or some other position, as long as the transmission is in 1st there will be no apply pressure to the TCC.

 

if i put the shifter in 1st, then there's no apply pressure to the TCC. i think we are splitting hairs. anyway, what would cause it to lock up continually?

 

I'd talk to whoever burned your chip.

 

If I had to guess, I'd say you've got a chip for a manual car, not an automatic. You might want to check the brake switch too.

 

I talked to alvin monday night at pcmforless, he said the chip is more than likely bad. He said about 1 out of 20 chips get corrupted but he isn't sure why. The high idle, speedo not working and the T/C staying locked up all the time is a tail tail sign of the chip being bad. A new one should be here tomorrow or Friday.


Jason