Hi all, please share your experiences with Code P0442, evaporative emission control system leak. My daughter filled her '05 Pontiac Sunfire with gas on Wednesday and got a check engine light on Friday. I ran my code reader on it this morning, and the only code was P0442. I checked the gas cap and re-tightened it. It did not appear to have been on loosely, but I expect the gas attendant stopped after the first 'click', so I went to the third for good measure. I did not cancel the code. She drove about 14 miles to an appointment this morning and then returned home (28 in total) but the CEL was still illuminated. I re-checked the gas cap and cancelled the code after reading a GM advice website. My question is, assuming a loose gas cap was the problem, would the CEL have gone out on its own and if so, after how long? Of course, if the CEL does not return then a loose gas cap was likely the problem, but if it does, then I'll have to further investigate. Anyone had a similar experience?

 

If the check light illuminates it will stay on for the 442 code. You have to go with a code reader and have it canceled. It will not cancel on itself. It is a Hard Code that doesn't reset itself automatically.

 

Yes, it will eventually go out on its own, it does not stay on forever. The self-resetting occurs provided the underlying cause is actually corrected and the test completes successfully the required number of times. It's usually an extended period of time for Fords (days, weeks, months, even). GMs are likely similar.

It's a heck of a lot faster to just reset it though and let it retest as per operating conditions.