Check Engine Light Keeps Coming On

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My CEL came on 2 weeks ago while driving on the highway. I had a guy @ autozone run a diagnostic with the cumputer and came up with the code: PO440 = Evaporative Emission control system malfunction
He told me that the most common cause was a loose or faulty gas cap so I bought a new one(after market) and he cleared the code for me. Then I filled my car up full w/gas to test the new cap and no CEL came on until 2 days later. Now its been on for about a week and a half and I dont think that its the gas cap. What else/where should I look for that could be a possible cause?

posted by  20ChevyCav00

That sounds familiuar to my situation. I have the mercury mystique, mine came on when I put gas in. then it whent off then came on like 40 miles later. It ended up being the vac hose. The light came on agian so it might be more than the vac hose. Ill tell you on wedsday but, I hope you have it fixed by then. :wink2:

posted by  Fgreco

check with gm for an upgraded cap.a loose wire on an emission control component can trigger an evap code too under certain conditions.this is what i would do: replace the cap with a gm part,fill the tank ,make sure the cap is tight ,disconnect the battery for 5 minutes.then see what happens after the battery is hooked up again.if it comes on again,check all the wiring going to all sensors on the engine.clean all the contacts with contact cleaner.

posted by  the lobster

Like lobster said it may only be a falty wire.

posted by  Fgreco

Model, year, engine, etc. More info is a definate must!

posted by  srober32

2000 Chevy Cavalier Coupe
4-cylinder 2.2 liter engine

posted by  20ChevyCav00

under your car to the right of the gas tank is the evap vent solenoid. it has a 2 wire connector with a pink and a white wire. the wires break at the body connector. this will set a p0440. you should be able to see the break. chevy usually stocks this harness.

posted by  DFgerbil

Or it could be a bad gas cap, or if you fill your car up while it is running you could get that code as well. :2cents:

posted by  srober32

I agree with everyone who said the gas cap. Sometimes if they dont crank the cap after filling it it will go on. I have one question how long does it stay on? Or should stay on? hours? days? :wink2:

posted by  Fgreco

I read just recently that the check engine light is an all inclusive emissions diagnosti, it is set off by an increase in the level of emissions put out by the vehicle, rings worn, a scratch on the cylinder wall, dirty injectors, or bad plug, or any number of things. this isn't much help to your situation but these hints may give you an idea where to look. A tune-up may solve the problem for a bit.

posted by  jackslap

A check engine light means just that, check your engine, it doesn't neccisarily mean you have a bad emissions system just that the computer picked up a fault with one of the sensors.

posted by  srober32

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