ECM issue

[Rfree]

Long story short. A few weeks ago I had the DEF Tank heater replaced at the local GMC dealer. Got it back, ran good for 3 days. on the 4th day truck would not start.
Had it towed into the dealer again. They are telling me my ECM does not match my truck. Said its vin locked to a 2016 LML. The truck is 100% stock any and all the work that has been done to it has been on at the local dealer including fluid changes. How could this be possible?
Also, they say the ECM is on nationwide back order.
Truck is a 2018 GMC 3500 Denali Dually with 120K miles on it. I've owned the truck since new.

 

[DAVe3283]

Do you keep the truck locked? Is it possible someone opened the hood and changed ECMs for whatever reason?

That seems less likely than the dealer being mistaken or your original ECM being corrupted for no reason. But people are doing weird things...

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[2004LB7]

Are the ecm connectors even compatible? What about the vin getting corrupt and somehow matching another LML? Shouldn't the dealership be able to flash over the current program despite being "locked"

 

[Chevy1925]

The dealer should be able to look at the prior ECM flashes/calibarations it has had. If you have brought it back and they have done ECM re-calibarations for anything within the ECM, they are stored on both the dealer side and in your ECM. if the ecm truely was swapped/stolen, they would see all the prior flashes/calibartions dont line up and it could confirm the stolen idea. Problem is, i dont see the ecm's swapping in.

if the ecm went corrupt, it is what it is. They will do strange things like the LML tcm's will do. you are also only getting what the service writer is telling you. The tech may be seeing on the mdi that the vin is kinda screwed up but giving a 10th digit that says its a 2016, then the tech explains this issue to the SW and he trys to dumb it down.

im not 100% sure they can do a full re-flash on an ecm with a corrupt vin. i believe if they can get it to read the trucks vin, they can but if its corrupt, it becomes a situation like trying to swap in a different ecm/tcm/bcm where you cant flash them to match the truck due to the vin mismatch.

 

[08lmm72mm]

Order a ECM from one of the tuner sites that does L5P tuning and take it to the dealer. Either that or sit with a broken truck until they are off backorder.