Vannin' Home

1995 g20 transmission control?

Posted By: Dw89xj

1995 g20 transmission control? - February 23rd 2019 1:22 pm

Are there any gurus in the group that can answer z couple questions? My vans transmission is in limp mode, it is an OBD1 style diagnostic plug. I bought an adapter and scanner with no luck and tried the paper clip jumper trick to try and get any codes, also with no luck. A refurbished -7427 pcm from acdelco is about 250 bucks, I can get one quite a bit cheaper but then would need to have prom/calpak transferred, before I spend this money can anyone tell me-
>Is the transmission control for the 4l60e in the pcm on this van or...
> is the transmission control separate and hidden somewhere else?
My van has pcm in the wall behind the driver seat, it's a conversion van. My speedo works fine, van runs pretty good considering the iac needs cleaned and it could use a tune-up in general. It's just the transmission is in limp mode, sometimes the CEL goes away and it shifts fine.
I was told that the pcm on this van controls the transmission and that it is known to have a ground that breaks and can cause this intermittent issue. It's mostly in limp mode now, occasionally it will act fine. Any help would be appreciated, my harness looks fine, plugs and connections look good. Speedo works. Since I cannot get codes and my transmission is in limp this tells me I'm losing power or ground somewhere, possibly the pcm issue I was told about? Again any help would be greatly appreciated. Again it's a 95 and has 4l60e and 5.7 tbi. Thank you guys.
Posted By: CatFish

Re: 1995 g20 transmission control? - February 23rd 2019 2:03 pm

I don't know very much but I'll share what I know.
Yes the PCM controls the shift solenoids. You should have two cables from the PCM. Red and Blue. The blue side has the trans pin-outs.
You said no codes? Mmmm.
Well, some things that cost very little and are easy to check.
Check your grounds. (of course) Both engine to frame and near the PCM.
Carefully remove, inspect and clean the transmission control cable and connector at the transmission. It's possible for that to get water,dirt inside.
Make sure the cable connections are clean and haven't corroded.

Pin-outs to check/trace your PCM grounds and the sensors grounds are here:
https://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/ecm-pin-out-chart-1

Hope this helps.
Posted By: Dw89xj

Re: 1995 g20 transmission control? - February 23rd 2019 2:13 pm

Originally Posted by CatFish
I don't know very much but I'll share what I know.
Yes the PCM controls the shift solenoids. You should have two cables from the PCM. Red and Blue. The blue side has the trans pin-outs.
You said no codes? Mmmm.
Well, some things that cost very little and are easy to check.
Check your grounds. (of course) Both engine to frame and near the PCM.
Carefully remove, inspect and clean the transmission control cable and connector at the transmission. It's possible for that to get water,dirt inside.
Make sure the cable connections are clean and haven't corroded.

Pin-outs to check/trace your PCM grounds and the sensors grounds are here:
https://troubleshootmyvehicle.com/gm/4.3L-5.0L-5.7L/ecm-pin-out-chart-1

Hope this helps.

Thank you very much this will help alot. Yeah the no power at the diagnosis port and obvious no power to the transmission have me leaning to a ground or pcm issue.
Posted By: MXDUDE

Re: 1995 g20 transmission control? - June 17th 2019 4:48 pm

Have you figured out this issue? My van had similar issues and determined it was the TPS.
© 2019 Vannin' Community and Forums