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Gas cap causes Check Engine light

2005 Malibu 2.2L 4 cyl.
109,000 miles

If I hit a bump too hard the Check Engine light comes on because the gas cap pops out. Dealer told me this is a common problem with many of the Chevy models earlier than 2007. GM doesn’t have a solution, either.

Since none of these cars have a locking mechanism I decided to get a locking cap at NAPA because the locking mechanism would hold the cap in place. Nope! The locking cap is even worse. I haven’t found anyone with a locking cap for this car.

I need some sage advice before my tank gets siphoned empty or the fuel pump goes bad.

Common problem?? You are the only one who has posted about it…If it was a “common problem” they would have to replace the filler necks and redesign the cap as it would be a big safety and emissions issue…

My M-I-L had an 05 Malibu (apparently it’s mine now, or at least mine to deal with). She just very recently passed, but in the last few years due to medical conditions, she found what had to be every pothole, bump and curb in town and hit them all…hard. Not once did her gas cap come off.

I can’t believe it’s a “common problem” that GM hasn’t found a fix for. There may be something damaged in the fuel filler neck due to a single improper filling or siphoning. I can’t really guess how it happened, but it shouldn’t be impossible to fix.

Try and invest some more time in figuring out what’s wrong, and fixing it.

I would suggesting taking it to a good local INDEPENDENT mechanic and have them take a look. I have a hard time buying the dealer’s story.

Thanx everyone for your comments!

I reread my owners manual today and, sure enough, it literally states that the filler cap can cause the Check Engine light to come on. The manual suggests turning off the engine then removing the filler cap and reinserting it twisting in a clockwise direction until at least three distinct clicks are heard.

This is what I have been doing and, yes, it does cause the Check Engine light to go off after a few minutes of driving but the next railroad track I cross causes the issue to come back.

I am planning to take the car to one of the trusted mechanics I have found and let them toy with the issue. Also, on the MalibuForums site someone who identiied himself as a Chevy service manager said to throw the problem back to GM because that part of the car is covered for 10 years regardless of ownership.

I’ll try my trusted mechanics first then get in line with others at the GM service desk.

how long have you had this problem? did it just started recently? if the problem just started recently, it could be that the filler neck, where the fuel cap screws on to is worn. the inside diameter of the threaded area where the cap screws onto was probably too large in design. so eventually it would wear out and/or expand with age. the only solution is to replace the filler neck or tank. or find a gas cap with a slightly larger thread size. i would take the old gas cap to the local parts house and try to find something that would fit. GOOD LUCK!

Every car will throw a code when the engine is run with the cap removed, it is part of the evap control system-- GM didn’t put it in the manual due to a “common problem” with their vehicles. My guess is something else is causing the check engine light problem, although a worn cap could be the culprit-- unlikely as you say you have tried other caps. Good luck!

It is common for a broken filler neck or fuel cap to cause a check engine light, yes. But it is not terribly common for them to break in the first place.

I’m having a hard time with the wording of your original post, have you tried a new gas cap?

Unless I missed something in your post, you haven’t tried an OEM replacement cap. That might be all you need.

Everyone I’ve taken the car to is baffled, too. The filler neck shows no sign of wear and no cracks, either. I bought three new caps; one from Chevy, one from NAPA and one from AutoZone. NAPA actually tried several caps, some with locks and some without a lock. On another forum a Chevy manager said AutoZone sells a locking cap made by an Israeli company that actually fits so I went to AutoZone and found the cap mentioned as well as several other models but none them fit as well as my OEM.

For now I’m preventing the check engine light issue by gluing a foam rubber inside the filler door which keeps the cap from popping out.

I’m still looking for a secure solution, too.

Have you considered changing the fill pipe?

Maxx ?


Sorry, I couldn’t sign-in yesterday afternoon…

It’s a 2005 Malibu Classic 2.2L 4 cyl.