Okay this is my first time working with this ecm or any gas engine at all with efilive. 2015 Denali 1500 6.2. Read the file off this truck, made some very minor changes and went to flash it back get the $06ff checksum error. even tried to just flash the exact unmodified file I read out back in, same thing. Truck is on an auction lot and is supposed to go thru this Tuesday, really need to get it back running. I have no history on this truck so no idea if there was any tuner on it on previously or anything. I have never had my v2 hooked up to anything but a Cummins, was doing this as a favor now im lost. I would really appreciate any help at all