TCC System

[Joe Kelsch]

My 99 Regal GS started acting funny the other day. The converter would lock up and disengage almost immediately. It does this at part throttle. The tranny goes through the gears alright and locks up fine initially. My buddy hooked his scan tool up and a code came back as P0742 TCC System Stuck On. The question is: can I run the car with this thing being broken? I also want to know where it is on the tranny and how hard is it to replace? Any help is appreciated.

 

[mikestertwo]

Sounds like the TCC solenoid is hanging up. That is a common problem. I have been getting that code on my 2000 Cadillac for the last 3 years I just haven't got around to changing it yet. The Cadillac has it's own built in diagnostics so I just clear the code when it comes up, which is usually every day. It doesn't seem to hurt anything, just makes it kind of sluggish under certain conditions. I'm not familiar with the trans in the 99' Buick so I couldn't tell you how to change it.

 

[SSedan64]

TCC solenoid is located on the side of the Valve Body inside trans & from the diagram looks to be a pain to replace. Should have a 4T65E Trans. If you go through all the trouble to replace it, get the Master solenoid kit that contains all of them 3-Shift, 1-TCC, 1-PWM.
May check the TPS sensor on throttle body, Manifold pressure sensor & connections etc.. before diging into trans. Maybe you'll get lucky.

 

[Joe Kelsch]

Thanks for the replies. Considering the time of year and that I don't have a garage, I'm not going to replace it anytime soon. And your right, if I'm going in there I'm replacing everything that I can, broken or not. I don't think its the TPS, only because it accelerates well, WOT or a part throttle acceleration. It only unlocks and locks during a cruise situation (I should've wrote this instead of part throttle). Is there a way to just disconnect the lock up? I'll just drive it with the convertor slipping all the time. My mileage will suffer, but it's better than driving my truck to work everyday (it's diesel and it only gets 18mpg highway).

 

[SSedan64]

There's not really a way to unplug just the TC solenoid like you can do on the older transmissions non (E) electronic control. There's just one big plug that has all the control sensor wires. It's not recommended to do it on the older trans either, can cause them to overheat.
A bad Brake light switch can cause TCC to act screwy also.

 

[Joe Kelsch]

You think I can drive it the way it is? Will it overheat? I'll take a look at the brake lights. Maybe there's a short somewhere.

 

[SSedan64]

Not sure Joe. I'm no trans expert by any means. Maybe someone with more trans knowledge will chime in.

 

[SSedan64]

Transmission Diagrams/Schematics

Joe if you'd like to look at a diagram of a 4T65E trans to see where the solenoids are go to this link. It has diagrams/schematics & part#'s for just about every trans made. It's a 47.2Mb Pdf. file so you may want to save it to your Harddrive if you plan to look at it very often. 4T65E starts on page 124, Electrical components pg.133. There are 944 pages in all. :biggrin: Welcome,Todd
http://dnlfiles.bf2guru.com/Ebay/PARTS CATALOG.pdf