VIN #s and programming

green02crew · Post by **green02crew** » Wed Jan 28, 2009 9:56 pm

Which VIN does the HPP3 read from, BCM, PCM or none of the above? If you change your BCM or PCM with a different model, for example I have had my PCM (and soon BCM) changed with one from another vehicle, does the HPP3 read the VIN that came from one or the other of these past vehicles?

So in theory, my PCM would have one VIN (although I think it had to be set to correct, not sure), my BCM another and my dash the correct one. I guess I'm just wondering if anyone knows how this all would work out?

On another note, I have 2 PCMs. If they have the same VIN (I don't remember if they do) and I programmed one, then swapped it out, set the other to stock to unlock the HPP3, then swapped the PCM again, would I have a programmed PCM and unlocked HPP3? Not that it would help much because then the tire sizes can't be switched from summer to winter without programming again, just curious overall.

04crewvt · Post by **04crewvt** » Wed Jan 28, 2009 11:09 pm

HPPIII reads the VIN from the PCM. I think the BCM will reprogram with the correct VIN when you do the reset(but I may be wrong). The programmer can only swap data. If you were to program one PCM and then hook it to the other, assuming it has the same VIN I would assume it will see the stock program and not reflash. Not sure why you would want to though. Don't you have a Wait4Me tune on one? If all you need is the different tire size programmed why don't you sent the stock PCM to him and have that one flashed as well for the other tire size? Unless you want to keep a stock one in case it needs to go to the dealers in which case I would just pick up another one and sell the HPPIII. That might be a bit silly having 3 around but would accomplish what you needed.

Post by **HenryJ** » Thu Jan 29, 2009 5:42 am

The HPPIII stores the stock data when it programs the performance tuning to your PCM. That is what it must match. If you go to another that has not been programmed, having the same PCM, I assume it would cause an error. Much the same as if the dealer were to reflash your programmed PCM. You would be stuck with a tuner that has the stock programming "plugging up the process."

green02crew · Post by **green02crew** » Thu Jan 29, 2009 6:16 am

Ok, it is beginning to make sense. Changes cannot be made to a PCM after the HPP3 has read/written its data or it will not match what the HPP3 had read previously thus causing a problem. It was just a thought in my head wondering how it would work.

04crewvt · Post by **04crewvt** » Thu Jan 29, 2009 6:32 am

Plus if you flash the PCM with the HPPIII that has previously been custom programmed (I don't see in the manual that you can just change tire size) you will loose some of the the benefit of the custom programming you purchased since it will now be stored as the stock program and the HPPIII program will be substituted for the values it is able to override.

Post by **HenryJ** » Thu Jan 29, 2009 7:02 am

green02crew wrote:Ok, it is beginning to make sense. Changes cannot be made to a PCM after the HPP3 has read/written its data or it will not match what the HPP3 had read previously thus causing a problem.

Not only match. The memory is full with the stock data.