12597120os to 12592618os

[SPRAYED07]

i have a 2007 classic silverado with the 1mg ecm (12597120os) I'd like to convert to a 2005 12592618os. is all i'll need an 05 pedal and tac module? what else would i need? can i even flash the 05 OS over my current calibration?

[GMPX]

You could, but the problem is GM tend to change modules between model years, so the cluster, HVAC etc on a 2007 'might' be different to the 2005, the problem is the 2005 OS's might have certain parameters or J1850 messages for the 2005 platform that won't work on your 2007.
In short the answer is, you could flash a 2005 OS in, there is no technical restriction as far as the PCM is concerned, it just might not behave 100% on the 2007 vehicle.

Cheers,
Ross

[SPRAYED07]

so if it doesn't behave correctly could the original os be flashed back in?

[SPRAYED07]

are there any custom os for the 12597120os?