Ask Ozzie: The Gas Cap and The Check Engine Light

So, what’s the relationship between your gas cap and your check engine light? I have, on occasion had to field this question: “Does removing my car’s gas cap while the engine is running trigger my check engine light?”

It’s actually a question that has one answer in two parts. First, with many of today’s modern cars, trucks, SUVs and vans this is often true. The gas cap might be the culprit, but cause is escaping vapors. If the fuel tank is between one quarter and three quarters full and the engine is running, the car’s emissions monitoring system will illuminate the “Check Engine”, or “Service Engine Soon”, or “Malfunction Indicator” lamp (depending on the vehicle) if it detects fuel vapors escaping into the atmosphere. So, yes, removing the gas cap will often cause the system to think it has detected a vapor leak.

Now if you are certain that your gas cap is secured, then you could be looking at a myriad of issues. While this particular warning light can indicate a vapor loss from your gas tank, it can also mean you are having a completely different issue. That’s why when your “Check Engine” light goes off, it’s a good idea bring your car in to your local dealer who can do a thorough inspection, fix and find your issue and TURN OFF THAT LIGHT! I know you don’t want to see it anymore.

Here’s something else that you may, or may not know. If you go for your Texas Vehicle Inspection and this light is illuminated, they will not inspect your car. You should be getting it checked ASAP as to prevent any long term damage to your vehicle.

Just some more friendly advice from your Grapevine, Southlake, Keller Buick GMC Dealer.