Check engine light - an 01 Jeep Cherokee

I have an 01 Cherokee with almost 80k miles on it. In the last two weeks the Check Engine light has come on. Both times had to do with a gas cap issue. Both occured the morning after I gassed up the night before. My mechanic says I need to buy a new gas cap from Jeep, that is the only way to stop it.

two questions.

1) How do turn off the CEL or is that something I have to have a mechanic do?

2) My mechanic says the way to stop this is to buy a new gas cap from a Jeep dealer. A cap from anywhere else won't fix it. Is this correct?

Between the times this light has come on, I filled up two other times without an incident.

Any help is appreciated.

Just buy a cap from the parts store...I got a locking Stant for 15 bucks.

Disconnect the battery to turn off the light. Or borrow the code checker from the Parts store.

Get a code if you can just to make sure it is the gas cap. The NSS will set a CEL with the mileage your Jeep has on it.

Alohabra:

As always, your input has been valuable.

I disconnected the battery and that got rid of the light. Thanks.

I am going to get a new gas cap this weekend. Will most auto parts stores carry them? Who would you suggest.

Thanks again.

P.S. How did come up with your handle on this site?

Any brand name store that carry Stant brand should have one.

Thanks Aloha.

I replaced the fuel cap and the light is back on. I believe the error code was "P0456-Evap Leak Monitor 0.020" Leak Detected".

I have a basic understanding of what the EVAP system is and what it does. I am just wondering, given the code above, what kind of money range am I looking at potentially to make this problem go away?

Thanks