Originally Posted by
B00STJUNKY
What's the concern/question?
Reading the ECM is harmless. When it says that 03-05 ECMs are Write Only, it implies that the MPVI doesn't read out the actual calibration from that year range of trucks. It reads some information from the PCM (such as OS ID, VIN, Serial Number, and a few other things to populate specific informational data), then it generates a stock calibration file for that ECM. After that, you can make changes to the generated file, and the flash the truck with the MPVI.