victimizati0n

Allright, i just got in my impala (2002, base) and the Check engine light is on.

My dad loosened the gas cap because out car makes this annoying sound, and he figured that loosining the gas cap would make the fuel pressure go down, maby stopping the sound.

The cap has been loose all week, and the light hasnt come on.

Do you think this check engine light could of been from the loose cap? And having low fuel pressure? If it is the reason, how do we get it to go away?

Thanks for the help.

blazee

You can go to autozone and get the codes scanned for free. A loose gas cap will set a code (usually P0440-Evap System) and turn on the light.

FYI: Loosening the gas cap doesn't lower fuel pressure.

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victimizati0n

Thanks, does advance auto parts have any? I dont know of any auto zones close to me.

ALso, thanks, i remember reading something on here that said that the check engine light would come on if the gas cap was loose cuz it would give the low fuel pressure thing.

blazee

I don't know if Advance does or not. You can check the location of nearby Autozones at http://www.autozone.com

More than likely the stored code is a result of the loose cap, you can just tightened the cap and the light should go out in a few days.

The reason a loose gas cap sets a code is because it makes the PCM think there is a leak in the EVAP system. The EVAP system is part of the emissions, it keeps gas vapor from being released into the atmosphere. The computer applies vacuum to the tank and monitors the rate at which the vacuum releases, by doing this it can detect a very small leak. With the gas cap loose the vacuum falls faster than the acceptable threshold and makes the computer think there is a large leak, it then sets the code to notify you that there is a leak in the system.

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victimizati0n

Thanks, my dad called me up, and said the light turned off, so i guess it was the gas cap

broil_me

if that light happens to come back..and you can find nothing else wrong...its probably something wrong in the programming of the computer(it thinks something is wrong when everything is ok)...my mom's '01 impala just had this problem...it cost like $100 total to diagnose/reprogram

victimizati0n

thanks, but it hasnt come back on since we tightened the gas cap.