Fault diagnosis device for detection device provided on engine

An engine ECU (100) executes a program including the steps of determining whether a combustion pressure in a specific cylinder is at least a predetermined value or not (S1000), determining whether there is an input from a crank angle sensor (104) or not, detecting a lacking tooth (S1200), determining whether the lacking tooth is in a correct position or not (S1300), determining that the crank angle sensor (104) is operating normally (S 1400) if the lacking tooth is in a correct position (YES in S 1300), and determining that the crank angle sensor (104) is operating abnormally (S 1800) if the lacking tooth is not in the correct position (NO in S 1300).