I am just wondering... a friend told me that a faulty gas cap can cause air in the tank.. is that true? also, can that cause the check engine light to come on?


1 Answer 1


There is always some air in the tank. The gas cap is part of the evaporative emission control system that is trying to prevent leaks of fuel vapor from escaping into the atmosphere.

Yes, it can cause the check engine light to come on. If you have a code reader you can plug into your ODBII port in the cab of your car there are some common codes that get thrown related to the evaporative emission control system.

  • P0440

  • P0455

  • P0442

  • If you don't have a code reader and have left the cap off, a CEL will go away in a few miles of driving with it correctly reattached. It's just one of the first things you check when the car seems to be running fine yet the CEL comes on, especially if you recently put fuel in your vehicle. Apr 13, 2015 at 20:42

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