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Q: Gas cap loose and check engine soon light comes on

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My gas cap says loose I replaced gas cap and it still says it and check engine light comes on what could be the problem

My car has 167000 miles.
My car has an automatic transmission.

A: Hi there. The vehicle’s computer can think ...

Hi there. The vehicle’s computer can think that the gas cap is loose simply from there being a leak in the EVAP system. This will occur if the gas cap neck is not sealing well to the cap, or if there is a leak someplace else in the system and the check engine light will keep coming on and off.

Smoke test the system to find the leak as it may be a solenoid or a small hose leak that can be hard to find. If you are planning on having this EVAP system problem checked, consider getting a certified mobile technician, such as one from YourMechanic, to come to your location and see why the check engine light keeps coming on. If you suspect that the problem is due to a loose gas cap, get the cap inspected as well.

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