Programming for speedo - 245/75R16 to 265/70R17

Ape0r · November 30, 2006

So, I put 265/70R17 tires on my truck, but I'm having trouble getting the speedometer programmed by the dealer.

I realize that GM likely won't have a code for that specific tire size, so I asked the service manager to try 265/75R16 (same OD), which was definitely an option on the '04 trucks.

The trouble is that when techline runs my VIN, they only get the code for the 245/75R16. The service manager is going to call back tomorrow and try again, and in the meantime I've compiled a list of other VIN numbers for him to try, mostly from Z71 Silverados and Tahoes.

The service manager has been awesome, but we're finding a dead end using my VIN. Can any of you dealership guys give any advice on how to get the appropriate code out of GM? Any problems with giving them an alternate VIN to get one?

Truck is in the sig, VIN is 1GCEK14TX4Z187002.

Thanks for the time,

Tom

GM-Tech · November 30, 2006

I'd say using a VIN from another vehicle may create other problems if you can even find one that Techline will accept. They obviously have something there to look up the acceptable tire sizes for the VIN given. I know of no way to fool them.

But here's someting else to think about. When you program the PCM to update the tire size, you're actually doing a complete reprogram of the PCM with a new calibration. It doesn't just go in and tweak tire size. What happens if the false VIN you're using has a different configuration/options than what's on your truck? Say, you have a 5.3 and the other truck has a 4.8. Or, there may be some other differences that you can't even imagine and would never think of to compare against yours. When you get done programming, it's conceivable that it won't even run!

I just don't think this is a good idea at all. Get one of those aftermarket scanners/devices that will allow you to put in whatever tire size you want.