2003 LB7 corrupt vin issue

[johnj]

Hi all. I tuned a truck for my boss several years ago and everything had been fine until the truck sat with dead batteries for a few months while the engine was replaced. Now it has a security light but starts and runs. When you try to flash it I get that the controller is locked with a custom key. Doing an obd read it shows the vin as a bunch of characters. So we replaced the ecm after doing some research on here and now this ecm has the same thing. Locked with a custom key message and the vin is corrupt. When I flashed the new ecm I used a known good dsp os that I had. What could be causing the corrupt vin?