LLY Duramax Tuning Fail

So I just got my 1st diesel ever, fairly new to HP tuners as well, but have other tuning experience.

Anyway I got my new new tow pig home and it's obviously not stock, doesn't run like stock runs a little to good honestly I'd like to turn it down a little.

Plug my MPVI3 in and no power, find a bad fuse no big deal I think I'll be good. Try to read the tune and it starts to act like its working, I'm seeing connections firing up, fail. I try to read the trans tune, same. I attempt a few more times and I realize I don't know enough to continue so I working on removing the rub strips and working on the paint a little and now I'm turning to the more experienced for help.

There's a good chance the radio is interfering with communication. I've seen even stock radios make problems, but usually aftermarket units are worse for that.

In the underhood fuse block, pull radio, radio amp (if equipped), and info fuses and try it again.

Some really stubborn trucks you have to find the communication splice pack and connect only to the module you're trying to work with.

One more thought. If the truck is already tuned, as you suspect, it could be tunerlocked, meaning that you won't be able to read it, no matter what you do, without knowing the key to unlock it.

I'll try the fuse tricks.

I've heard of that stuff before, and the locked tune but I always thought in the past that was to write a tune, I was unaware that was just to even read it, wow.

So for the sake of argument let's say it's locked...now I what, I could deal for now maybe, but one day I'll be just flat out done with that...I guess the only answer is to purchase a new ecm? Is there no way to blank this one out and then load a stock tune out of another truck?

Also if one had said key how do you enter that?

It's actually more common for reading to be blocked than writing. For example, if the truck has an Efilive custom operating system, you won't be able to read it, but you can write a tune. If it is a specific lock with a custom key, both reading and writing are blocked. I have heard of some guys getting around the lock with a bench flash, but I can't speak to that personally.

I thought there is a field to enter a custom key when you're reading the tune, but maybe I'm mistaken. I'm much more familiar with Efilive, and they definitely have that option.

Yes they lock to keep their intellectual property safe, so people don't copy their work, and sell as their own etc. Single tune EFI if unlocked you could read. If its got a DSP5 switch you wont be able to read it (changes the OS of the ecm). Simple way is to have it flashed back to stock, then read and modify from there. Dealers can do it and many others. Could bench flash it as well.

My 04 LB7 was stubborn. I had to flash a few times for the mods to take.

I haven't seen a tune switch anywhere, but I have been covered up and haven't had a chance to try pulling the fuses and reading it again...I have the bed off of it right now, removing the trashed gooseneck, and installing a lift pump.