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Q: Check Engine Light Reappears

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I had my check engine light come on in March . I had a shop do a smoke test .They replaced gas cap and a sensor .Not even a month later light was back on . This SUV is running fine and I just put new plugs in it . The light went off today . My buddy told me if tanks gets around 1/4 the required test will not be performed and the light will go out . My question is , I had a older Expedition and it was the same issue .Always having the light on and money out my pocket .I just want to know , are these issues usually fixable or am I looking at battling this Check Engine Light forever . I just rather trade the SUV in

My car has 119000 miles.
My car has an automatic transmission.

A: The mechanic that did the previous work and...

The mechanic that did the previous work and did a smoke test was doing the correct thing to detect the leak. The only thing is all the leaks were not identified. Have the vehicle tested again and make sure all the tank hoses and fuel fill pipe are tested for leaks. Make sure after any repair is done the system is retested with smoke to verify no other leaks are found. If the problem still exists after this, or you just want to get a second opinion on the cause of the check engine light, you can book an appointment with a different professional technician, such as one from YourMechanic.

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