Originally Posted by white_noyez
I remember a while ago i thought i saw a thread about this but i couldnt find it in the search. My buddy has a 2004 chevy 1500 and the "tighten gas cap" warning keeps coming up on his screen but it is perfectly tight. Whats the cure for this?? thanks
I know this thread is a bit old, but I wanted to pass along an easy fix for this problem for others to use.
My 2006 Silverado started showing the Tighten Gas Cap
light on my dashboard after I took a long trip in the truck. Up until this point, I've never had any warning lights with this truck. I've heard of this problem with other car/truck owners, who had less than satisfactory outcomes. Naturally, I tightened the gas cap about 20 times, but no luck. I examined the gas cap, and it looked fine. I read my owners manual, that basically told me that the warning light (orange indicator) should go out after a few key starts. After tightening the gas cap, it would go a few days, but sure enough the DIC warning would appear again. Eventually, the warning light (orange) did clear, but a few days later, I would get the "tighten gas cap" DIC warning again and then the warning light (orange) would lock in.
Consequently, I was dreading taking my truck back to the Stealership
, so they could dream up more problems and hand me a bill. As a last ditch effort, I bought a Haynes manual and read about the Evaporative System on my truck. The gas cap DIC warning is part of the evaporative system to reclaim gas vapors. The onboard computer on the truck monitors the gas tank vapor pressure, which checks for vapor leaks in the fuel system. The warning involves a pressure mismatch, which the onboard computer relates to a fuel vapor leak. It assumes fuel vapors are escaping via your gas cap thus circumventing the purpose of the evaporative system.
I fixed the problem by dipping my finger into cap full of motor oil and applying the oil to the gas cap gasket. Poof! Problem solved.
The gasket on the gas cap gets dry (probably due to overfilling the gas tank once) and over time the seal drys out. By re-lubricating the gas cap gasket, it once again seals properly. If the gasket on your gas cap is torn, or cracked, then get a new gas cap.