Recalibrating speedo in 2009 1500 Sierra

ChevyTech77 · April 9, 2012

GM didn't make a truck with that size tire on it therefore, they don't have a calibration for that size to put in your truck. If they produced a truck like yours with a factory, or accessory, tire in that size then yes, you could have a GM dealer calibrate the truck for that change. Buy an aftermarket programmer and do it yourself.

By my math currently, your speedo is showing 2 mph slow at 60 mph.

Doug_Scott · April 9, 2012

Sounds like you may have been lied to my friend. No reason they should not be able to do it....Like stated above, there are many hand helds you can do it with. What would the dealer charge in the ones they can do? It may be worth it to just get yourself a tuner, do it on your own and whil you have it, install a tune. It will only make your truck run better, nothign to worry about.

Dealer cannot do it. I posted this in 2010 that they cannot after I had tried to get it done. The techline needs to do it, and provide the dealer with some new code.

Now, what they can do is set the tire size. But only to a size that was offered on your truck.

You post in contradicting...

So in other words you are saying the dealer CAN do it, just like I stated. They get the information they need and the dealership does it.

When the dealership told him they can't do it, he was lied to. They just don't want to have to go through the steps of getting it done.

What I said was the dealer could not correct my speedo due to my changing to 4.10 gears. Techline will not give the dealer the updated code for a gear change.

The OP happens to have tires that are the same diameter as the 265/70/17 tires that were an option. The dealer can alter the tire size setting, but are limited to using tire sizes that are factory available on that vehicle. The dealer cannot set the computer to the actual tire size the OP has. This is not hard to understand.

ChevyTech77 · April 9, 2012

Techline can alter the calibrations for a gear ratio change under the same circumstances as tire changes. If the vehicle was available from the factory with the gear ratio (standerd equipment or option) that you are looking to calibrate the vehicle for, they can calibrate the vehicle for that change. Not available with that gear ratio? No calibration.

Doug_Scott · April 9, 2012

They refused even doing it for 3.73 gears. They told my dealer they would not provide support for gear changes due to not having all the required pieces that you would get on a factory order with those gears.