Yesterday i had a light come on below my guages saying that my gas cap wasn't closed. A guy at the auto parts told me to get a new one, after trying to tighten the cap didn't work. But this evening as I was driving the service engine soon light came onwhile the gas cap light was still on. My question is are the two related or could it be something more to cause the engine light to come on?

 

try taking ur negative terminal off the battery for 5 minutes to clear everything, see if it comes back then.

u can take it to autozone they will tell u the code for free

 

When the service engine soon light comes on because of the gas cap, it takes a little while for it to go off again once you tighten the cap. Maybe a couple of short trips.