Gas cylinoid/Check engine light

Car: 2003 Impala/107,000

On my drive into work today my check engine light came on. As usual I paniced, and stoped in at a local Auto zone to have the code read. Code showed an issue with a cylinoid that regulates the air in the gas tank or something, basically the guy said. He asked if I had just gotten gas recently, I did but it was last friday night, he said to check the gas cap and I did and it wasn’t secure. It was on but a tight seal wasn’t made. He said that could be causing the problem.

How is this possible? Could a loose gas cap cause the CEL to go off and show this kinda code? Also, wouldn’t htat happen pretty quickly? I got gas friday night, and since then have droven maybe 60 miles, most on Saturday, didn’t drive the car on Sunday and then just back and forth to work yesterday and then I was about half way into work today when the CEL came on. The guy said if that was the issue that the CEL should go off after driving the car for a while and the seal is on tight…is that true?

Yes…a loose gas cap can cause a CEL to trigger. What was your specific code? The CEL might not trigger for some time so I think a loose gas cap in your case was the culprit. Did your CEL finally go off?

Also, when you put in gas, do NOT “top-off”, that will also cause similar problems, but much more expensive to fix.

I only drove about a half of a mile since tightening it to get to work, will drive about 13 miles home tonight so hopefully go off then.

My concern is I ususally put the cap back on tight nad make sure to do that, so kinda concerned if someone in my neighborhood is screwing with my car.

“So kinda concerned if someone in my neighborhood is screwing with my car.”

It’s possible. My security camera caught my neighbor’s kid trying to steal gas from my wife’s car. I showed the video to the neighbor and he took away his kid’s 4-wheeler away for a month. He finally apologized for his actions after he got his 4-wheeler back.

Why is it important for the gas cap to be tight?

The gas cap must be tight to allow the system to function in a “closed loop” instead of an “open loop” as it is when the gas cap is missing or loose. The gas vapor system is monitored by the vehicle computer for various reasons. The “closed loop” approach is also mandated by the government to protect the atmosphere from fuel vapors.

thanks, now that the cap is secure, any idea how many miles/time I will have to drive for the CEL to turn off?

Not really…if it’s a gas cap problem…it should go away in a couple of days. It all depends on how many miles you drive. You can also get the CEL reset at Auto Zone if their scanner has that ability. Make sure to write down the codes before you reset the light.

They said they could not reset, so hoping the cap was the problem and that the light will go off.

Solenoid not cylinoid

The CEL will go out after the computer tests the EVAP system 2-3 times and finds no problems.
The car needs to be sitting unused for several hours before the test is done.
The gas tank also needs to be in a certain range of fullness.
That’s why the light didn’t go on for several days after getting gas: the tank was too full to do the test.

Well it will be sitting for about 8+ hours today while I am in the office working, then will drive home tonight which is about a 13 mile/45 minute drive home in city traffic. The tank was filled almost full when I got gas on friday, and with the driving I did it is now near half a tan so guessing that is when it did it’s check.

It varies somewhat by car manufacturer but the evaporative emissions tests are often performed only under certain conditions (e.g. fuel tank fill level in a defined range, certain operating conditions be met, etc). It takes several instances of a failure test result to trigger the light and it also takes several instances of passing result to extinguish it.

I just hope that was it and it’s not the cylinoid going bad…

It only takes a very tiny gap/hole to register as a small evap leak. If the gas cap was loose at all, that was most likely the cause versus an evap solenoid failing

Oh it was loose, now I am just worried if I didn’t put it on tight last friday or if I have someone in my neighborhood screwing with my car at night.

OK, it was solenoid the OP was talking about…

"OK, it was solenoid the OP was talking about… "

Yeah, it also took me a while to figure that out.