2007 Corvette 6L80 Problems

[village_idiot]

Watching via HPT or a Snap-On scanner, when you shift the car from Park to D, the scanner will show a Current Gear of 4 sitting still.

It will drive with 4th through 6th gears. Using the scanner, you can command 1,2,3, etc and drive the car with all forward gears.

If you shift from Park to D and the current gear shows "4", and then you touch a paddle to try to down shift it to 1st, watching the scanner it will immediately spazz and cycle 1-2-3-4 so fast you can barely read the numbers. To get it out of this, you have to power off, and start over.

Some back story on this...

- Early this year, I was attempting to tune this car, and it had this problem. I sent it to a dealership so they could diagnose wiring, modules, trans, etc. They said it had metal in the fluid, and needed a trans rebuilt. The owner chose to pay their diag. fee and use a trans shop for the build vs dealership.

- He has a friend of ours with a shop R&R the trans, trans shop bench built it. Converter cut open and freshened up... Same problem.

- Trans builder says the TCM is bad, so the owner orders another one, has the dealer flash it to stock specs... Same problem.

- We checked all the wiring from the ECM to the TCM (continuity tests good, and nothing looks damaged), pulled the trans, and the builder went back through it. He said the front pump failed a test and replaced it. The owner decided to buy a Circle D billet converter at this time to have everything brand new. Installed everything again... Same problem.

This problem has not changed.... original trans vs built, original TCM vs reman replacement, prior stall converter vs brand new circle d...

Since it can be COMMANDED into 1st, I'm led to believe that this is a wiring/module issue, and maybe the former burnt trans was collateral damage of driving it like this?

What should be checked next? What's being overlooked?

[blindsquirrel]

Weird... there's no fault condition where it defaults to 4th. Fault while in 1/2/3 defaults to 3rd, 4/5/6 defaults to 5th.

I'd almost be tempted to temporarily cut the tapshift signal wire (ckt 5526) just to get peace of mind that it wasn't being asked to do something silly.

[village_idiot]

Squirrel I forgot that step. Its been unpinned from the TCM plug, and was eventually pinned back. Same behavior pinned vs unpinned

[blindsquirrel]

Well you don't know until you know and now you know so...

Don't have any U codes anywhere, do you? And don't have any that've been sneakily disabled in the list?

[blindsquirrel]

Have you verified it maintains B+ at pin 12 (IGN1), backprobed or as near the trans connector as you can get?

[village_idiot]

No current codes, and I pulled a compare file earlier to verify. Current deletes are
Rear o2
Front o2 delay (headers)
Both cats
Po101, 106, 121 disabled
Misfire disabled 1200 and below (cammed)

All trans DTC are stock, and on stock TCM tune

It doesnt even have any BCM fault codes

[village_idiot]

We can check pin 12 tomorrow. I believe it has been checked, but it wont hurt to go over it again

[village_idiot]

Any possibility of a corrupt file causing this? I have not performed a write entire back to stock with a known good file. This car was tuned by a shop for bolt on mods...owner drove it for an unknown to me amount of time, then got a cam kit and stall....then I plugged into it for the first time. It's had this issue since the first time I scanned it.

[blindsquirrel]

I know the TCM should be write-entireable with HPT but with mystery crap like this I'd want to start over with SPS.

I coulda sworn that yesterday I saw a bulletin or something about symptoms after a corrupted programming event, can't find it again now.

[village_idiot]

The TCM portion is freshly dealer flashed (has a couple hours of key on/off, park/drive gear changes on it)? Do you think its worth it at this point to trailer to the dealer, and pay for the dealer flash on the ECM side? I dont have the flash tools for that

[HardH20]

I had this same issue a couple of months ago. Drove me nuts. Was tuning a 06 that just had headers put on.

Your issue is in the ecm tune somewhere. I tried to back tune mine-work backwards in layers of things I changed. Got frustrated and started the whole damn thing over. Stock file and just deleted rear O2 for headers. Super basic. Now trans worked fine. Rebuilt the tune and it didn't happen again. I believe it is somewhere in the torque management settings in the ecm side. Your trans and tcm are fine.

[sevinn]

The issue is more than likely in the torque management settings on the engine side. Care to share the tune?