Check Engine Lite - Loose Gas Cap

[Smitty]

So yesterday my check engine light came on (I have about 43,000 miles on my vibe). I had heard that having a loose gas cap can cause it to happen, so I checked mine, and sure enough it was significantly loose. Relieved that it was a simple problem, I got back in my car and proceeded to drive around town, expecting the light to go off... unfortunately it didn't. I know sometimes you have to disconnect the battery to get the CEL to clear, but I was wondering if anyone else has had this problem and had it clear automatically. If so, did it immediately clear, or did it clear after a few trips. Also, if I take it to autozone or somewhere to have them read the CEL code for me, what will it likely read if it was the gas cap that caused the problem.Thanks for the help,Smitty

[tnpartsguy]

Yeah, once the 'gas cap code' sets, you have to use a TECH2 or the autozone toy to reset it. Some dealers will reset it for free one time.

[joatmon]

Since you found the gas cap loose, it would be a good assumption that it was the cause of the CEL. a loose gas cap would likely cause one of the various evaporative emissions controls CEL codes, like P0440, P0441, P0442. There is no one code that can only be caused by a loose gas cap.There is some sort of trip cycle defined in the service manual, (which is not where I am right now or I'd quote it), and when the system goes through some number of these cycles without detecting the error condition, it will clear the CEL by itself. I can't remember the details, something like five times in a row start cold and run to operating temperature without the error.If you hadn't found the "significantly loose" gas cap, then I'd say go get the code read soon, but since it was loose, assume you've fixed it for now, drive normally, and just wait for the light to go out.

[tnpartsguy]

5 cold start-to-warm-to cold again cycles, or 120 mile trip, but that doesn't always clear it either.

[Mavrik]

Well it will clear eventually on you after a few cycles of start ups, the exact number I'm not sure but it will clear. If not, your dealer with a tech II or a garage with a code reader should be able to clear that P0440 code no prob.