POST #38.......found the issue.

So, this Level 4 - 4L80E has been in my 1998 Trans Am for 4 years and running perfect, zero issues. Its only been behind about 420 RWHP the whole time.

The only thing that was done was a new engine was installed. Installer said all he did was lower it a little bit to help get the new engine in. The Frost 4L80E-to-1998-PCM adapter cable was never unplugged or touched.

Now its throwing these codes:
P0753 Shift solenoid "A" electrical
P1810 Transmission fluid pressure valve position switch circuit Malfunction
P0713 Transmission fluid temperature Sensor "A" circuit High Output
PLUS......the tranny shop also got a: MAF sensor code but I don;t know which exactly it was.

The tranny shop dropped my pan to look for any issues with wiring and found nthing wrong. Looked at the external wiring and plug end and found nothing wrong. They also installed two new shift solenoids to rule that out.

Transmission feels totally normal taking off from a start and feels solid all the way to 50-60 mph, no slipping, but will not shift out of 2nd gear.

Any ideas what the heck could be causing this?

 

When you unplug the connector on a 4l80 it stays in second. I’d check that it’s actually getting power since all solenoids are ground activated.

 

Multiple electrical codes is going to be an electrical problem with trans, wiring harness or pcm no other options , Assuming trans not opened and harness plug no damaged leaves car harness, pcm , fuses.

 

The connector is firmly plugged in. I assume the tranny shop unplugged it to check the pins or for fluid shorting out the connection. But they said they looked at every wire inside the pan and outside the tranny.

Its going to another shop tomorrow. He's going to check inside that main plug to see if there's fluid. But also check the Frost adapter cable all the way to where it plugs into the harness that goes to the PCM.

.

 

Yea, my transmission builder said the same thing as you, he's just 250 miles from me. I expect shops, especially a tranny shop, to have done a power check. This new shop i'm tryimng hopefully knows how to check for proper power.

Whats the easiest way to confirm the tranny is getting power?

And would I also get codes for the two speed sensors and other items if they were not getting power?

 

When you say PCM........

The tuner who put the base/street tune in it so I could break the engine in said the transmission was communicating normally while tuning. So does that rule out the PCM being bad.

Something odd he said. He said it was saying 4L60E on his software. But 4 years ago when the transmission went in the tuner did the 4L80E segment swap in my 1998 PCM and its been normal ever since. How could my PCM have switched back to 4L60E segment on its own while sitting without power for weeks waiting for the new engine to go in?

 

the power for the solenoids doesn’t come from the connector it comes from the fuse box. It only passes through the connector. Having it plugged it just means it’s plugged in. Check upstream of the connector.

 

probably going off the vin. The vin can say it’s a 60 but the tune still has the 80 segment.
you really need to find better shops to spend your money at.

 

I looked everywhere for any fuses associated with the transmission.

which fuses should I be checking for power delivery to the tranny?

 

The new tuner thought the problem was that is had not been segment swapped to the 80E. I told him yes it was, 4 years ago by the original tuner. He said it was showing 60E.

He said he had to perform the 80E segment swap to my PCM again. He than drive it again and the shifting issue was still there.

I wish there were better shops down here.

A member came to my house two days ago to buy my Huron Speed T4 kit. He seems to know a LOT about all this stuff but he lives 1.5 hours north of me.

 

 

4l80es mechanically stay in second gear when the electronics are not functional. Going down some rabbit hole with the tune is likely a waste of time.
it’s probably a wiring problem. But it’s almost as hard to diagnose this sort of thing over the internet as it is giving a hair cut.

 

Everything was working until you got the new tune?

 

As soon as the engine installer was done and started the car for the first time it had the P0753 shift solenoid code. I towed it to a tuner who than saw that same code while he was driving it doing a base (break-in) tune. And it wouldn;t shift out of 2nd when he was driving it.

I took it to a transmission shop that everyone recommended, they saw all 4 codes on their scanner. The 3 listed in my original post here plus a MAF code.

Its looking more like the engine installer crushed a wire, or maybe he didn't and it happened while the engine was coming out at a different shop, or maybe I did something while moving the harness around while the engine was out doing other little things.

If the connector on the transmission can be unplugged, then checked right there for power, seems like the first step to have done.

 

Ok thanks. I'll print it out for the next guy who will be looking at it. It seems around here shops either only do rebuilds or shops that only do electrical issues. Monday I'll give it to a guy that says he can do both. We'll see.

 

Big issue is shops do not want to troubleshoot trans built by others and at least with trans shops they are in it to sell trans builds and see trouble shooting as a waste of time. Tuners generally would rather stick to just tuning and mostly engine tuning. You would be amazed at the number fo tuners I have worked with who really are pretty lost with the trans area of tuning and well do not care to learn it.
And most Trans shops are not into mods and performance builds and are pretty much lost in all areas on this from the build to the tune.
NO OFFENSE TUNERS OUT THERE MANY OF YOU I HAVE WORKED WITH OVER THE YEARS ARE GREAT. SOME TRANS SHOPS ARE GREAT TOO.

Also mamny just are not sure how to charge for diagnostics and many customers also dont want to pay for such they are only willing to pay for the fix, But Indeed is someone spends 5 hours tracking down what an issue is even if it ends up being a 5 dollar part that takes 5 minutes to install they still deserve compensation for the time diagnosing.

If It was myself diagnosing your issue , The first thing I would do after scanning for codes and watching data to determine if commands are correct would be to hook up a simple control box I made to control the trans with switches, presure control and TCC operation capabilites and or course gear selection and operate the trans with it through various conditions and take it off the table or prove its to blame one or the other to give me direction in diagnostics on where to go next, Then assuming it took the trans off the table and tune commands off I would then troubleshoot each wire going to the various solenoids using a device with LED I made that lighty up when a command if given to each solenoid, For instance in first on a 4l80e it would light up sol A and not light up for solenoid B in 1st gear and then each additional gear as commands were given by PCM
1st on off
2nd off off
3rd off on
4th on on

Then if those all showed ok I would next check input voltage and drop accross the solenoids . This one may seem silly but I have seen where at rest I had 13.8 v at PIN E but when the solenoids starting turning on the voltage dropped to as I remember 9.7 with both solenoids on in a 4l80e which should have been 4th but was not, This turned out to a be an ignition switch issue. But also another time had similar sympton and the way I found it was when applieD the measurement across the solenoid of voltage should remain 13.8v but instead it became a much lower voltage which pointed to a ground issue I later tracked to a wire that while bolted in place the area had been painted and the paint acted as an insulator to ground, (This is also why I remove all paint from mounting surfaces of the trans to block etc before shipping or having other pick them up )

HOPING THIS MAY HELP SOME but as mentioned trying to troubleshoot an issue like yours over the net is like trying to eat a burger over it lol.

 

Well……while my old engine was out I did paint my entire engine bay. Is there any specific ground that attaches to the engine bay metal surfaces that’s the important one?

I can think of three grounds I can check. The other grounds on the back of the head are tight, they were checked.

Thanks for the post though. If you were near me I’d tow it to you.

 

I turn away any automatics that need tuning because it’s too much of a hassle and everyone wants a different feel. The juice ain’t worth the squeeze.
it sucks for people that need that work done, but such is the world we live in.

 

The main transmission harness connector can be plugged in upside-down. It'll plug in fine but will throw all sorts of codes.

 

When this 80E went in 4 yrs ago that’s all that was done. A tuner went for a 15 min ride with me, did his thing. That was it. Perfect all 4 years.

This is a product of my new engine going in. Hopefully by the end of this next week it’s done.