I keep getting a tighten gas cap warning on my 2004 Chevy PU, any ideas how to fix it?

Question

I've replaced the cap and had the code cleared, but it keeps returning

Answer 1

Have you replaced the cap with one from the GM dealer? If not I would try that first. If the code comes back after that, then it means there is a very large leak in the Evaporative Emissions System. This system, on your vehicle, has a consumer feature added to help you from having to go to a repair facility when you accidentally leave your gas cap loose. If this is not the problem, then it means there is a very large leak somewhere else in the system. If the PCM detects this gross of a leak, then it will automatically assume the gas cap as the most likely culprit, although this is only an inference and it cannot actually monitor the gas cap. I recommend taking it to a facility for them to evaluate the cause of the concern if you have already tried the OE cap. Aftermarket caps do not have a good success rate of sealing the system properly.

Answer 2

try tightening the cap first.