rpm's in cold weather

I have a 05' sierra with a 5.3 liter 4x4. My question is now that the weather has turned cold (below 40) my truck now runs 200 rpm's faster at an idle and at highway speed even after the engine and tranny are hot. And it is now lowering my gas mileage. Is this normal or is there something i can do. Thank you forany help.

I would query your dealer on this, maybe a scan or some update may reveal the problem if any, this is a warranty issue anyway.

There is a TSB that may correct this condition..it also includes a PCM calibration update..
This is covered under your factory warranty.

There is a TSB that may correct this condition..it also includes a PCM calibration update..
This is covered under your factory warranty.
Thanks for the advice. Ihad the truck to the dealer yesterday and no suprise they could not find any TSB's or any codes. Is there a referance number or anything I can tell them to get them on the right track? thanks for any help you might have.

Have them reference TSB#05-06-04-063
One of the concerns it covers is an incorrect idle speed condition..like I said it MAY correct the condition you are experiancing