I recently purchased new tires for my 03 GMC 2500HD Duramax Diesel. The stock size is 245/75 and I moved up to a 285/75. This changed the ratio on my speedometer, Driver info Center, and Odometer. The DIC cannot correctly calculate MPG, range, or average fuel economy anymore, also the speedometer is about 8 mph off. Is there a chip I can change or reprogram the ECM to accomidate the new tire size?
Sincerely
Shawn Timothy

I recently purchased new tires for my 03 GMC 2500HD Duramax Diesel. The stock size is 245/75 and I moved up to a 285/75. This changed the ratio on my speedometer, Driver info Center, and Odometer. The DIC cannot correctly calculate MPG, range, or average fuel economy anymore, also the speedometer is about 8 mph off. Is there a chip I can change or reprogram the ECM to accomidate the new tire size?
Sincerely
Shawn Timothy

Shawn,

I suspect by now you've received an answer to your question or have sold your truck. But, if not, maybe I can help. I just bought a 2002 Chevy Silverado HD and it came with a Superchips module for reprogramming my on board computer. Having read the accompanying material with the Superchips module, it mentions changing the on board computer if you upgrade your tires. I've never done it, but looks like it can be done. I offer two options; either buy a "Superchips" module (look at their website superchips.com) or go to a dealer and ask them to reprogram your computer to compensate for the bigger tires. Heck, if superchips can reprogram your computer, I'm sure the dealer can too. Hope this helps.

Tg