The contact owns a 2015 Ford Explorer. The contact stated that while driving at an undisclosed speed, a carbon monoxide odor was detected coming from the cabin air vents, which caused the contact and his passenger to have headaches. The vehicle had previously been serviced by the dealer for the recurring failure. The dealer had diagnosed the vehicle with an unknown failure, and an unknown part was replaced; however, the failure recurred. The dealer was made aware of the failure and scheduled an upcoming appointment for diagnostic testing. The manufacturer was made aware of the failure and opened a case. The manufacturer referred the contact to file a complaint with the NHTSA. The failure mileage was approximately 86,000.