Disclosed is a hydrocarbon sensor diagnosis system including a computer programmed to collect data from a hydrocarbon sensor 12hc while an exhaust gas recirculation system 20 is in an open state. The hydrocarbon sensor is mounted along an engine air intake 16 between an exhaust port 18 of the exhaust gas recirculation system 20 and an intake port 22 of a cylinder head 24. The computer is further programmed to determine whether or not a hydrocarbon sensor fault exists based at least on the collected data. The determination may also be based on ambient air temperature or temperature of a cylinder head of an internal combustion engine supplied by the intake port of the cylinder head. The system may be for use in an autonomous vehicle and allows for the diagnosis of hydrocarbon sensors necessary in governmental regulations.