1995 BONNEVILLE SE

I had a used transmission put into my car two months ago and had intermittent problems where it wouldn't shift into overdrive. I would pull off the road and turn the car off and start back up and the overdrive would work again.

I read about problems with the TCC selenoid or valve body cross leaking on this forum so I told the transmission guy to install another transmission in my car because there was a problem with the one he put in.

I just received my car again whith another transmission in it (from a wreck, but in good shape) and it worked well for two days. Now it'* starting to have the same problem where sometimes it won't shift into overdrive. I think it'* mainly when the car is warmed up.

I know it'* not the transmission now, could it be the PCM?

Anyone have any ideas what would cause this, the electrical connections are clean.

Thanks for any info ....

There was a GM service bulletin about a similar TCC problem, and the cause of the problem was a chafed wire in the harness that connects to the tranny...but that problem was only documented for the '91-'93 4T60-E transmission. To fix that problem, the wiring harness needed to be replaced.

Both my friend Phil'* 1995 SLE and my 1994 SLE have this same problem.
So, swapping the Supercharged 1993 Park Avenue Ultra'* tranny into my 1994 won't solve the problem?
How hard is it to change the harness?
Buy new from GM or get one from a salvage yard?

I hear everyone talking about scan tools .... can I buy one somewhere and do it myself?
I'm quite mechanical but I don't have any of these speciality tools like scanners. If I can get one for a reasonable price, how much would one cost and what is a good make/model to get for my 95 bonny se?

If the problem turns out to be the PCM, where is it located and how much is a replacement? Also I hear people talking about replacing some chip or module which gives you better performance. Can you give me some info on that as well? Maybe a price and model to purchase.

Thanks again......