Need 4L80E help

[Slapperbar]

Here's the scoop. It's the trans. in my 1991 Sub. The trans is acting like a 3 speed when it's below 40 deg. F.
No lock up or fourth gear. Sometimes when the truck has warmed up I can remove the Trans and both ECU fuses and reset the computer getting full function back. It is NOT throwing any codes. I think it's a 'noid, just don't know witch one.
The late model harness connector was put in before I bought it 6 years ago.

 

[Slapperbar]

Anyone? ANYONE?

 

[kauzenkaos]

do u got a scan tool

 

[Slapperbar]

My buddy does have an OTC diagnostic tool. No codes.

 

[cuervo]

You know you can not get trans codes with the normal scanner. I had to take mine to a trans shop and he had a scanner about the size of a loaf of bread that got them.


My 91 4L80e had an issue with OD. I did a lot of reading and one suggestion was to unbolt the fuse box connector inside the engine bay and spray some electical connector cleaner in there, let it dry and blot it back up. That didn't work for me.

The trans had a two bad sylenoids and 3 codes. They replace the 1/2 gear sylenoid and the manifold pressure sylenoid and all was well for about 6 months and it started to lose OD again. This time they replaced the computer and it's been fine for about a year.

edit

Here is a link to my trans thread http://coloradok5.com/forums/showthread.php?t=246152

I'm not sure if your issues are the same. I will also say that you can not get the trans codes with the key or a normal OBD1 scanner.

Good luck

 

[Slapperbar]

Thanks for the link.
What was used was a OTC super read everything ever made computer.

 

[kauzenkaos]

when i get back to work on monday ill look up the the info on urs but ull need a scanner that you can view trans data on and yes the super otc will do just that

 

[cuervo]

Did you have any luck fixing this issue?

 

[Slapperbar]

It'll go to a shop soon. I'm in a Apt. for the time being 'till we buy our house. Just starting the new job and all. So work in the parkinglot is out. Besides, all of my tools are at my parents house 2 hrs away.

 

[Slapperbar]

As an update. It went to the shop last week. 2 codes, 24 & 28. Low speed sensor voltage and bad pressure sensor. It was "serviced" by Cottman before I bought it, so who knows what the updated wiring harness looks like inside.

 

[Thunder]

24 may be an issue with your VSS
28 Is usually the pressure switch in the trans.
If the pressure switch is bad it wont let it in OD or lock up the TC. It may also be causing the #24 but not sure about that. Fairly cheap easy fix but you do have to drop the trans pan.

 

[Slapperbar]

We're shooting 28 first for that very reason. Also a front driveshaft re-spline/ re-build.

 

[Slapperbar]

So... It lives again. The problem was not the pressure switch. 2 of the 3 wires to it were shorted up by the computer. It has a new switch in it now also.
All fixed.