Front Seat Heater/cooler problems of the 2015 GMC Sierra

The contact owns a 2015 GMC Sierra. While driving approximately 60 mph, the vehicle began to vibrate. The longer the vehicle was driven, the more it shook. The contact took the vehicle to the dealer several times, but no failure was found. The dealer test drove the vehicle and it did not vibrate. The dealer replaced the tires, transmission, and shocks; however,, the failure recurred. The vehicle was not repaired. The contact stated the seat warmers also failed. The manufacturer was not made aware of the failures. The approximate failure mileage was 2,500.