I saw your reply under the "Dear John" post. I had the same problem with the Mazda gas cap. Forgive my poorly written post.. trying to type before I have a meeting.
Here is my story, in case it is helpful to you at all. At first, the check engine light would come on and I was told that my gas cap wasn't tightening enough (or something similar to that.. this was over a year ago). They'd clear the computer and the check engine light went away. this happened a couple of times. What ended up happening is that some valve in the gas cap/gas tank wasn't closing and when I put gas in my car, my car didn't start afterwards and I had to leave it at the gas station. when mechanics tried it a few hours later, it started up fine. this happened twice. The second time I said "oh no, this happened the very last time I put gas in my car". (lightbulb)
So, had the car towed to the dealership, it started up fine a few hours later but since it happened twice, we had them look into it. As I mentioned, some valve wasn't closing... apparently this valve closes after you pump your gas and pushes all the harmful fumes to the engine for the engine to burn when you start your car. Because the valve wouldn't close, the engine wouldn't start. The car would start after a few hours because the fumes would settle and the valve would close.
MY POINT (sorry this took so long) - you might want to have them check the valves in your gas tank to make sure this isn't what's happening to you, because if you are not near home and your car won't start, it's a downer. Hope this is helpful!
Re: NewQueen- Mazda gas cap
I had a Nissan with the same problem... Every.single.time I got gas in NJ the gas light would come on, because they werent tightening it as much as I did when I pumped myself. Or if I lazily put it back on. Basically if I didn't tighten it to the point of it feeling like it was about to break, the gas light came on.
Dealership did a billion things to attempt to fix it (and charge me accordingly) only to end up saying they didn't know what the issue was and I'd basically just to have to deal with it.
I did the same as you, had a friend turn the light off everytime it came on. It was always the same error.
Wow - so many times I haven't been able to replicate a problem at the mechanic's, but I never thought to record it. Definitely using that idea in the future!