For the last 6 months or so I have been getting the "Check Gas Cap" message in the message area. You get it every time you start the car and when you clear it out about every 15 minutes there after. What causes this and where is the sensor located? 2005 V6.

 

Make sure you put the gas cap on all the way. It should "click" a couple of times when you turn it

 

Yeah, yeah, yeah. Didn't think I had to mention that I know how to put a gas cap on.

 

Haha, you'd be surprised at some people who come on here. But anyways, my guess would be to buy a new gas cap. My co-worker's 2003 pontiac had a crack in it and is was messing up the car.

 

Lots of people bring that same thing up and don't realize you have to twist the cap until it clicks several times. I would never "assume" that you had done that, especially with the way you phrased your issue - you don't mention if you have double checked the cap to make sure it is tight, and that is one of the reasons that you will get the check light coming on despite clearing it.

 

The 'sensor' you are looking for is under the trunk area
outside the vehicle. Its part of the Emmissions System
You should have a DTC stored telling you whats going on
better than the 'idiot light' gas cap icon.
The system is not sealed for one reason or another.
The most common driver error that makes the light come
on is a loose gas cap. Beyond that, there are many other
determining factors that ALSO make the light come on.
A new gas cap is about all YOU can do and other than
that, its stealership time if that dont work. Sorry...