evaporative fuel system leak

Asked by Apr 02, 2013 at 05:00 PM about the 1998 Pontiac Grand Prix 2 Dr GT Coupe

Question type: Maintenance & Repair

My 1998 grand prix GTP is throwing a code for evaporative fuel system leak. I have replaced the gas cap
and the code went away for a while and came back. What else could be causing this condition?

5 Answers


A code P0442 most likely means one or more of the following has happened: - A loose or improperly affixed gas cap - A non-conforming gas cap (i.e. not factory/original brand) - A small leak/hole in a fuel vapor hose/tube - Other small leak in EVAP system - Faulty vent o-ring seal

5 people found this helpful.

I have the same problem...I have had my car in and they "smoked it"...found no leak...they have done this twice...I have replaced my gas cap twice....I leave and the light is off---next time I turn on my car the light comes back on and it says "check gas cap"...how can I find the leak? this is getting very costly and don't have the problem solved yet...

27 people found this helpful.

Mine is a pontiac Grand Prix 06 supercharge. An I'm having same problems. Last week I had to replace my something intake on my engine oil was coming out my engine where it wasn't sapose too. And my engine light came on and now it's back on but this time on my screen it pops up "check gas cap" and the mechanic said it's my evap system.

10 people found this helpful.

yes, I figured out that it is the evap system and the canister rusts out...many people could not figure it out, but I went to a car dealer and the service guy had the same problem in his car ...checked mine and it was....I paid and haven't had any trouble since...and now I even get better gas mileage...amazing!

15 people found this helpful.

I took my car to a smog check shop and they ran it through there computer and it said I ha a EVAC systems leak detected (large leak) I had a brand new fuel pump put in and the guy who put it in forgot to put on the rubber seal the goes around the fuel tank and the fuel pump. When I road around the block know problem. But when I road it about 20 miles. The light turn on. I told the smog shop owner what he did and doesn't think that the problem. Any answer from anybody.

2 people found this helpful.

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