Gas Cap Throwing a Check Engine Light? [Diagnose & Fix]

If your gas cap is causing a check engine light there could be a few different reasons why. Sometimes it’s the way it has been put on, and other times it’s because of the gas cap itself. Watch the video below or read on and we’ll explain how a gas cap can turn on your check engine light and how to fix it.

Signs the Gas Cap Needs to Be Replaced

Check Engine Light

The gas cap will throw a check engine light if it needs to be replaced. Sometimes it’s just how the cap has been placed, and other times it’s because the cap is defective.

Gas tanks are designed to contain a certain amount of vacuum pressure. Sensors on your car monitor this level of pressure. If the vacuum pressure drops beneath a certain threshold, the car will signal the check engine light. The first part to check is the gas cap to confirm it’s not releasing pressure. A faulty gas cap can throw the following codes:

  • P0440
  • P0441
  • P0442
  • P0443
  • P0446
  • P0453
  • P0455
  • P0456
Fix a check engine light from a gas cap yourself with quality auto parts at 1aauto.com

Why Gas Caps Fail and What to Check For

1. Gas Cap Is Not Secured

Sometimes a gas cap throws a check engine light because it wasn’t properly secured after being removed. This usually happens at places like a gas station. If you fill up your gas tank and a check engine light comes on after you drive away, it could be from an improperly secured gas cap. To prevent this, always turn the gas cap until it clicks.

2. Broken Gas Cap Seal

Gas cap with broken seal

Gas cap seals or gaskets help keep vacuum pressure inside the gas tank, but when damaged, they can leak pressure. Gas cap gaskets can roll over, fall off, break, crack, and split, all creating opportunity for leaks.

Sometimes the gas cap can break on its own by clicking and looking like it’s snug but never sealing.

3. Incorrect Gas Cap

Two different gas caps

Not all gas caps are the same and they can vary in shape and size. If the wrong one has been installed, it’s not going to secure properly and will throw a check engine light.

How to Fix a Gas Cap Throwing a Check Engine Light

If you need to replace the gas cap, they can be installed quickly and easily. The repair usually requires the removal of an old one and the attachment of a new one. Some gas caps may have a tether to remove as well.

Check out this video to see how easy it is to replace a gas cap. Find how-to videos for your vehicle in 1A Auto’s how-to video library.

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