I just read out an 09 sierra e38 ECM with a few TCMs to get the OS# of the different TCMs i have to see what i can use.

Anyway the first read was good. the next read however, i got the error message saying "unable to validate VCM". Ive read on here that that error pops up for vehicle that are not supported by HP tuners.

Weird thing is that my ECM read out fine earlier today and the only thing ive have done was swapped the TCMs. Any ideas why this is happening?

Also, i am bench reading these computers.

Thanks