HELP Programming issue

[TBMSport]

The dealer is programming the TCM in the truck and it is refusing to take. The tech is explaining that the GM computer website is pulling up the truck's ECM and rejecting the VIN being downloaded into the TCM. He cannot 'build' the TCM VIN because of this.

Any ideas on how to wipe the TCM clean and make it ignore the ECM VIN?

[TBMSport]

Perhaps more specifically...can anyone explain how the TCM to ECM 'rewrite' process works?

[Taz]

Sorry ... not 100% clear on the problem, and therefore possible solutions. Would rewriting the VIN in the ECM and / or TCM to the required make / model appease the dealer ? If so, this is easy to do.


Regards,
Taz

[Taz]

Or do you mean the CVN / Checksum data ? See thread below for more info on those ...

http://forum.efilive.com/showthread....&highlight=cvn

Regards,
Taz

[TBMSport]

The problem is the TCM is not engaging ANY gears. There is communication with both, but as the E67 ECM OS isn't normally compatible with the T43 OS, we're attempting to rebuild the T43 with a VIN that has a T43. The technician is stating that no matter what, the TCM keeps pulling up the ECM's VIN and not the one he is manually overriding. Is it he doesn't know what he's doing or is there a special procedure?

[Taz]

Do mainly Gen IIIs ... Gen IVs are a little out of my "comfort" zone ! You can program the ECM and TCM with the same VIN - EFILive does really care what the VIN is (except for the scanner perhaps). So, find a VIN that you think will work for this issue, and enter it in the ECM and TCM - that way no matter what the technician scans, the VIN you want will be "found".

Once you have finished, then you can put the VIN back to what you want.

Regards,
Taz

[TBMSport]

I'm not using EFILive. The truck is at the dealership and they are using GM scan tools.

[Taz]

OK .. don't know your relationship with the dealer, or if they could / would temporarily change VINs for you to allow software to load .. will leave that with you.

If you end up coming back another day ... can enter the VIN that you believe will work using EFILive in both the ECM & TCM. I'm not sure this will overcome the issue the dealership is having, but it's one more variable that you can eliminate.

Regards,
Taz

[ScarabEpic22]

Jesse, the VIN is irrelevant except when scanning enhanced PIDs. Ive heard the Tech II uses it to pull the latest OS from the GM servers. Ive put a random VIN in my TCM for kicks, truck started and drove exactly as before. As for the 'TCM to ECM rewrite', that would be impossible as the 2 modules have very different hardware and will not accept a tune from a non-compatible module. But if you mean how the ECM uses the tables in the TCM, Im honestly not sure. The trick here is going to be finding a TCM OS that will properly communicate the gear status and everything to the ECM.

[TBMSport]

I think I figured out the problem. The situation was the already programmed TCM from another used tranny was put in my truck without reflashing and went into LIMP MODE (Park Reverse Neutral 3rd). Once we reflashed it, all gears were lost. I thought it was a VIN issue. It then hit me that the Park/Neutral wire was not connected to the ECM. Therefore I believe that even though we did a swap from one truck to another without a reflash, the memory in the TCM already established reference points for gear engagement. In the reflash, that memory was wiped clean and therefore has no reference whatsoever, so it's simply not engaging gears to be safe....hence go past LIMP MODE and straight to total shut down.