I heard it's actually two clicks...but who's counting?
Yes, as people have pointed out, it can throw a cel. I believe it's due to the pressure in the gas line. My local dealer says you'd be surprised at how many people come in with that just to realize that's the cause.
Gas cap CEL?
I had a gas cap CEL when I used an aftermarket gas cap. I do not know. None of those who I know has had no gas cap cel but mine. This is what happened to me: when I got CEL a day after swapping gas cap, the Longo mechanic swapped vacuum tube(?) for $125 and CEL went off. Next day, CEL came back on and went to dealer again. This time, CEL went off, free of charge. When CEL came back on for third time, I was kind of mad and talked to general manager guy and then talked to a different mechanic. This time, the mechanic asked me where is the original gas cap and the reason of swapping to aftermarket one. "Won't allow smog check," I lied...lol. I brought the stock one back and the gas cap CEL never came on. That is what happened