Gas cap sabotaged by dodgy mechanic or is this commonplace?
 

I have a request for help here so I can determine if something I noticed about my gas cap gasket on my '02 T & C is normal/commonplace or if somebody (say a less than scrupulous mechanic) might have intentionally done this to cause the check engine light to illuminate. A little background first.

I was leaving my work parking lot on my way home from work this past Tuesday afternoon and the check engine light illuminated not long after I left the lot. I researched common causes of this by Googling around and found that I could pull up the diagnostic code display on the odometer by switching the ignition switch off and on several times. I successfully pulled the codes and found that the problem code indicated a small leak in the evaporative emission system was detected (P 0456 I think it was). The suggested fixes were to check that the gas cap was on tight first. I checked the gas cap was seated properly but the problem persisted until today so I examined it more closely this morning.

I popped the gas cap off and started examining it and saw a black rubber gasket/ring-seal around the inside of it. I started looking at this seal and I noticed it seems to have a slit running all the way around the outside of its entire circumference. The seal ring is a hollow tube as I can see because the slit is clean through the outer circumference wall of it. It appears to be a relatively clean break/slit. It doesn't look like it got dry rotted and cracked or something and the ring is otherwise intact. So my question is, can somebody else who owns a Town and Country around approximately the same year as mine check the ring seal on their gas cap and tell me what you see? Is your like this too? Is it normal?

If this is not normal, is this a common problem for these cars? Or did the mechanic at the shop I last went to do this knowing that after a short while it would cause the engine light to come on bringing me back in to the shop again? I suspect them because nobody else has worked on the car but the shop in my neighborhood and I last had it in maybe only a month or two ago to have the oil changed and a loud grinding/vibrating noise fixed which according to them turned out to be a problem with some kind of seal in the power steering system having disintegrated and particulated bits of debris into the fluid reservoir or some such thing like that. That also started happening shortly after the previous time I had it in there. But then again, the car is 8 years old so I'm willing to give the benefit of the doubt somewhat but this gas cap thing looks too intentional to be just 'wear and tear.' I can only conclude that this is how the seal ring is supposed to look or else somebody intentionally cut it.

Also, if it turns out this gas cap gasket is bad, anybody know of a good place I can just buy a replacement gasket without having to buy a whole new gas cap?

Sounds like the seal split, these caps don't last forever. A cap with seal should be about $8 at a local parts store. I would just get a new cap and be done with it. My mom's 01 Camry just needed a new cap for the same problem you suggest. Either the seal goes bad or the venting mechanism quits working.