The airbag light has come on for the third time. the problem is in a sensor in the seatbelt. each time it is the same problem and porsche wants me to spend $550 to replace the unit with the fourth sensor. i have declined to do this as they will not warranty the new unit. this is a well known defect in this car according to servicemen and there are similar complaints on your website. i have called and written to porsche without response. *ln