my daughters GTO had the CEL light on at about 1400 miles on the odo. I told her to take of the gas cap and put it back on with two/three klicks, she did and the light went off.
Today (1700 miles on the odo) she told me (I`m in Germany - daughter is in Santa Barbara/Ca) the light came on yesterday again and not after a refill because her tank was about 3/4 full, she tried again with the gas cap but didn`t work this time.
Today or tomorrow she`ll let check this out by a Pontiac-dealer in SB, I`ll let you know!!!!!