jeeptjstud

I was driving my dads 96 12v automatic on a 2500 miles trip and everything was fine. All of a sudden it started shifting funny, lost overdrive (light on button went off and stayed off) and the gen light came on. It is now stuck in 3rd gear (drive). Once the truck turns off it is difficult to get it back up into 3rd gear (drive) as it shift sporadically. Swapped the alternator and still no fix so we measured the voltage and the Alternator was reading 12v so we installed an external voltage regulator which fixed the charging issue but still have tranny issues.

The tach, speedo, ac, etc all still work.

Does this sound like a PCM being that the shifting and voltage regulator pooped out at the exact same time?

Lary Ellis (Top)

My 96 did that it was the TPS Throttle. Position Sensor, put a new one in and all is well.

AlpineRAM

Well, this is a little tricky...

OK, we know that the PCM is doing something (a lot) wrong.
Now we have either a bad PCM ($$$$) or maybe something that makes the PCM flip.
I'd suggest to check the wiring first, see if there are chafed cables shoring to ground, or bad connectors.
Then, if the PCM is in a good mood, I'd try to get error codes out of it.
This can help you find the true culprit.
(I had a Chrysler 300C in the shop where Chrysler had authorised the 4th transmission swap in 8 k miles on warranty.... a thorough analysis showed the car needed a new battery and one ground wire replaced... )
So, in my opinion, Lary's problem was fixed by the TPS, but yours may well be something else.

ecmexchange

That might be the problem.
Give us a call so we can help you troubleshoot the problem. 1 888-875-2958