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Q: The check engine light often comes on and goes off after a well.

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The check engine light often comes on and goes off after a while. Any time I notice it whiles driving, I park and close the fuel tank well but the light doesn't go off. Sometimes I restart the car but it still won't go off. It goes off on it own and comes back after some time. What could be the cause?

My car has 137531 miles.
My car has an automatic transmission.

A: When the Check Engine Light comes on, that ...

When the Check Engine Light comes on, that means that Trouble Codes, likely identifying the causes of the issue you are having, have been stored in your car's computer. The fastest way to resolve this is to have a Check Engine Light Diagnostic performed to obtain those Codes and start to track down the possibilities. Such a Diagnostic can be done by a certified Mechanic from YourMechanic on a mobile basis. The Codes are downloadable using a scanner and they should indicate at least the general area of the fault. A possibility is that some engine management system has a poor electrical connection or other wiring problem that is evidencing itself only intermittently. But, there are other possible causes of intermittent illumination of the Check Engine Light such as failures in engine sensors, intermittent misfires, and faults with sticky or stuck valves such as in the EGR (exhaust gas recirculation) system or the EVAP system. The best thing to do is get a Check Engine Light Diagnostic and then it will be clearer as to what segment of the engine controls needs to be looked at in more detail.

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