Tl* the contact owns a 2003 gmc yukon. while driving 55 mph, a loud bang was heard as the contact noticed that the rear tailgate glass shattered. upon starting the vehicle, the contact remembered that the rear defogger was turned on; however, she was unsure if it was on at the time the glass shattered. there were no warning indicators illuminated. the vehicle was taken to an independent mechanic where the rear tailgate glass was replaced. the cause of the failure was unknown. the vehicle was not taken to a dealer. the manufacturer was made aware of the failure and a case was opened. the contact was informed that there were no recalls. the approximate failure mileage was 225,000.