I have a 2002 mustang
gt convertible with 70K miles. The service engine light comes on sporadically typically several days after I reset it. The code is PO442 and the light usually comes on when I get the car to higher speeds, 80-110 mph (mechanic tells me this is a coincidence and it doesn’t help with the diagnosis). The gas cap has been replaced and a mechanic could not find a vacuum leak or any issue with a hose. Mechanic suggests replacing celluloid. Anyone seen this type of problem before?