My girlfriend recently leased a new Z3 2.3. It's a gorgeous car and a joy to drive, but ... it's been back to the dealer for service three times so far (it has about 1700 miles on the odometer). The check engine light came on the first time at around 700-800 miles. She took the car in to her dealer, and one of the service managers told her (get this!) that she was putting the gas cap on wrong. Well, this didn't really insult or infuriate her the first or second time, but after the third time (she got the car back on Friday and the light was back on Saturday), she got pretty torqued. Somewhere along the line they have told her that it might be the charcoal cannister or some "loose hoses". She has had it in for the third time, and so far the light has stayed off.
As far as I can tell, the service manager she's dealing with is a condescending nitwit. If there is some problem with the gas cap gasket not seating (?) and causing a trouble code, then replace the gasket. I can't understand their game, but I'd sure like to hear if anyone out their has had a problem with their Z3 and the engine light coming on repeatedly. I'm not familiar with BMWs - I just clunk around in my Toyota pickup (which, BTW, has never had a trouble code in 106,500 miles).