Missing Gas Cap

Someone stole my gas cap about a week ago. Around the same time my check engine light came on. I went to the dealership and they said that the missing cap was the reason the light when on so I bought a new cap. The light has not gone out yet. How long do I wait to bring the car back in to see if there is something else making the light stay on. I dont want to pay the $50 diagnostic fee at my dealership to find out that nothing is wrong? Does anyone have any suggestions?
Thanks!

Well There is another free thing you can try.. I think you should disconnect the battery for about 10 mins. THen connect it again. Drive it around for a couple days. lets hope that works. What disconnecting that battery does is resets the computer.

Hope that helps
DD

actually disconnect it for 2 hrs 10 mins doesnt give it enough time. first try the negative charge on ur battery

just keep driving it the computer need to see the evap test passed 50 times before it will turn the light off so it might take a while. if you don't want to see the light on anymore go to autozone and get them to reset it for free. you can't reset the light by disconecting the battery like you could in the good old days you need a scan tool