Quote Originally Posted by GMPX View Post
Yes and no Howard.
The 2006/2007 should be fine, worst that will happen with a 2008 is the VIN will get corrupted and the Crank Relearn will need to be done.
Thinking about it, 12597121 probably covers 2006-2007, 12612384 is for 2008.
I've never been able to flash an 08 calibration into a 121 ECM. Haven't tried working it backwards.

Tried flashing a '10 truck cal into a junk 455 ECM (broken retaining tab) and it took the calibration fine, EFILive couldn't retrieve the calibration though.