Q: Check engine light on due to gas cap.

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Hello. I am having an issue with my check engine light. I went to Autozone to have a computer diagnositic check, and they said it was the gas cap. Bought a new gas cap, went off for a bit, then came back on. I went back, they told me to tighten it and drive and it would reset itself. I drove from NY to CT and back and it is still on. Not sure what to do and I have inspection coming up. What is the average price to fix something like this?

My car has 93000 miles.
My car has an automatic transmission.

You should have your fuel vapor control system for leaks by a mechanic that can fill the system with smoke from a smoke machine that helps to locate the leak in the system. The purge control valve is the most common cause of a leak in the system next to the gas cap. After running these tests, the technician should be able to find what needs to be repaired and estimate the cost to fix it.

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