When i started the vehicle, the "check engine light" came on. this has happened once before a year or more ago. i brought it to a dealer and he asked whether i had gotten gas recently. yes, about 200 miles and 2 weeks ago. he checked the gas cap and it was laying in the gas filling area, not screwed in at all. obviously it had come loose somehow. he checked the computer and something like "gas line vacume" came up. he screwed in the gas cap. easy fix, but since this has happened twice now with the same car and i have had dozens of cars and driven hundreds of thousands of miles and never had this problem, i wonder if it is an issue that needs to be looked at...