I had my original PCM flashed and bought a new one to swap out if need for smog, at that time. The mechanic said he had forgot to burn in my current mileage at the time so it sounded like it was going to start from 0. I swapped out the reflash for new (process took about 10 minutes with bat disconn), and with the new OE installed, it retained my original mileage, the truck remembered the true mileage and transferred it to the new PCM. I was hoping that the new PCM would only remember the actual mileage it accrued, and not the vehicles, for a low mileage PCM resale. Guess it doesn't really matter, but I'm curious to know how the truck transferred the mileage to the new PCM?