Hello,
I have a similar problem with a 2007 Hyundai Elantra using the MS906 in which I can't seem to write a VIN onto a used/replacement ECM. The original ECM is reporting a ROM issue and is causing the check engine light to come on. The car starts and drives fine with the replacement ECM and the check engine light stays off, but the entire problem is just that is has the wrong VIN (the one of the car that this ECM came from in the junkyard).
I found that by tricking the tool into thinking the VIN is blank by turning off the ignition just before pressing WRITE VIN, it brings up the box to enter the new VIN. Once I type in the new VIN, before pressing OK, I then turn the ignition back on (otherwise it tells me it can't establish connection) and it seems to proceed as if it will actually write the VIN but then it says the write has failed.
I wonder if there's some way, a "trick", that could actually get this tool to write the VIN to a used ECM that already has a VIN on it. Right now it definitely seems this Autel model (all of them?) can only write VIN to an ECM that does not have a VIN already on it ... in other words, only a new "blank" ECM.
Thank you for any help.