tighten fuel cap light stays on

http://www.smogtips.com/check-engine-light-turn-on-off.cfm. best bet is to take it to a mechanice so he can use a device called a battery tender. This is plugged into the cigar lighter socket before you disconnect the power and ground cables to not only hold the radio station presets, clock settings but also keep the on-board memory alive for the power-train control module (PCM).

I am having the same issue. Gas cap light comes on and pending code P0455. Changed cannister purge valve, vent valve, has cap, fuel tank pressure sensor. Had a snoke test done, no leaks. Still the light comes on. What else could it possibly be???? I'm at my wits end.

I just had oil change and light was on code 455 showed man suggested a 69$ flush where he took off the vent tube at brake booster and put in some chemical that goes into engine and freezes carbons and they burn out tailpipe. My light went out right afterwards , he then ask me about gas cap . It comes loose all the time he recommends I replace it but from all I have read that makes no difference but the flush sure did !

Solved: I had the same problem, gas cap warning light followed by engine light on my 2006 trailblazer LS. I ordered a new "trailblazer" gas cap from amazon and replaced the cap. But the gas cap warning light cam on again followed by engine light and stayed on. After inspecting the gas cap, i noticed it was a little flimsy and didn't fit flush and was too easy to com loose. So I went to O'Riley Auto Parts a bought a standard gas cap that was a lot more sturdy and had a flush fit. The Engine Light shut off later that night and has not returned. problem solved!