returning truck to stock - mainly ecu?

[cdub2010]

Long story short i have a poorly performing 6 litre swap in a 08 yukon, i purchased it, i didnt do any of the work on it. I want to pull out the 6 litre 4l80e combo and swap in a stock 5.3/4l60e and just use it as a driver. Who to use for the ecm change back to stock? Will a dealer touch it, can a hot rod shop reflash it? I cant find my info on who did the tune in it now. Might just be easier to part out instead of dealing with the problems. Anyone got any insight?

[mongocanfly]

What's wrong with the 6.0?
It may just need a good tune..preferably a dyno tune..

When you say (6 litre swap in a 08 yukon) I'm not following...is this the original engine? In a 08 yukon? Or has the engine been swapped before?

[LS short box]

I don't see a dealer helping you out. Nothing against dealers but to retro fit an engine and trans that's just what they don't do.
If you are going to get a 5.3/4L60E out of the salvage yard make sure you get the ECM so then you shouldn't need to reflash it.
Times two on take it to a tuner to see what you have. Then decide.

[Joyridin]

That seems like a lot of work for nothing...and I mean nothing. Get the engine tuned correctly and you should have no issues unless somebody threw in a large cam.

I don't know of any dealer that will touch it especially i it isn't stock. On top of that, by today's standards, that is a pretty old set-up.

[Pulse_GTO]

If the engine is in a 2008, and it originally came with a 5.3/4L65E combo, the dealer may be able to flash the ECM and TCM back to factory specifications. Also you may want to make sure that the transmission wiring is correct for when you go back to the 4L65E. The 2008 Tahoe came with the E38 ECM and a separate T42 TCM in the transmission. The T42 was used on 4-speed transmissions and the T43 was used on 6 speed transmissions.

If you have an indipendent shop flash it back to stock using aftermarket software (i.e. HP Tuners or EFI Live), make sure that they first download the file that is currently in your ECM and change that back to stock by comparing values to a known stock file and copying them over to the downloaded file, save the file with a new name and upload the changes. Simply writing over a file from a different vehicle could cause the ECM to brick, VIN to be incorrect and the immobilizer to not allow the vehicle to start.

Do you know if it was even tuned after the swap? Again an independent shop can download your current tune and compare it to a know stock tune and see what changes, if any, have been made. If none have been made, then the shop or individual can copy the parameters over from a stock 6.0 file and it probably will run much better.