I have a recurrent problem that is triggering a check engine light. It has been in the shop multiple times and they can't find the problem. However, I think I have finally detected a pattern, and want to know if you can tell me what it means.The error code is the same code that you get if you leave the fuel cap off, an evaporative emissions code. I don't remember right now exactly which one.However, if I clear the code, it will not trigger again if I keep the fuel tank above 1/4 full. It is only when the tank is 1/4 full or less that the code gets thrown.If you need the actual code, it will take me several days to drive the fuel level down to where the code is thrown again.Thanks for any input.

I've had a car throw a code when I didn't have the fuel cap screwed on tightly enough. Is there any chance it's a faulty cap? Might be a cheap try just to put on a new cap and see if that fixes it.

I had to replace the hoses on our Durango years ago that run from the gas tank to the EVAP canister if I'm remembering the term right. It was throwing the loose gas cap code. The short section of hose was very brittle and falling apart while other rubber hoses were like new.

Take it to a shop that has an evap smoke machine. Make sure it has less than a 1/4 tank. The shop will hook up the machine and pump smoke in the system. Eventually the smoke will exit through the leak, and become obvious where the problem lies. This is the definitive test for such issues.The likely candidates might be evap canister, filler tube, vent hose.

Not knowing what your vehicle is I would also suspect the EVAP canister and related parts.

Had the same issue with my 2010 F-150. It was some sort of EVAP solenoid that went bad that they had to replace. Took a smoke machine to find it. It was a simple swap/replace after that. Definitely wouldn't find it on my own.

Check Engine Light | Good Sam Community

18 Replies

Bobbo
Explorer III
Dec 01, 2013
OP here. The car is an 04 Chrysler Town & Country minivan. It is not a loose gas cap. One of the things we tried was a new OEM gas cap, but that didn't help. This problem is at least 4 years old, so it can't be the result of new work. It was my Mother's car, and she finally just started ignoring it. She passed away on November 7, and I am getting it ready to sell so I would like to track this problem down.

I will find a garage that has a smoke machine and take it there.

Thanks all.
Krusty
Nomad II
Dec 01, 2013
Have you had any recent repairs? ie: fuel pump replaced? I find that usually the tougher to find leaks are from the top of the fuel tank, fuel pump o ring etc.
Chuck_thehammer
Explorer
Dec 01, 2013
you may have a bad EVAP valve or a cracked hose. in you EVAP system.

without replacing everything.. a smoke machine is the only way (cheaper) of finding the problem.
call around the shops as NOT all have the smoke machine.. and just start replacing parts.

retired auto mechanic, 43 years.
jus2shy
Explorer
Dec 01, 2013
Had the same issue with my 2010 F-150. It was some sort of EVAP solenoid that went bad that they had to replace. Took a smoke machine to find it. It was a simple swap/replace after that. Definitely wouldn't find it on my own.
rrupert
Explorer
Dec 01, 2013
Not knowing what your vehicle is I would also suspect the EVAP canister and related parts.
Vulcaneer
Explorer
Dec 01, 2013
Take it to a shop that has an evap smoke machine. Make sure it has less than a 1/4 tank. The shop will hook up the machine and pump smoke in the system. Eventually the smoke will exit through the leak, and become obvious where the problem lies. This is the definitive test for such issues.

The likely candidates might be evap canister, filler tube, vent hose.
Hannibal
Explorer
Dec 01, 2013
I had to replace the hoses on our Durango years ago that run from the gas tank to the EVAP canister if I'm remembering the term right. It was throwing the loose gas cap code. The short section of hose was very brittle and falling apart while other rubber hoses were like new.
pfidahospud
Explorer
Dec 01, 2013
I've had a car throw a code when I didn't have the fuel cap screwed on tightly enough. Is there any chance it's a faulty cap? Might be a cheap try just to put on a new cap and see if that fixes it.

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