CONTROLLER FOR INTERNAL COMBUSTION ENGINE

A controller for an internal combustion engine is provided. A control circuit performs active control for an air-fuel ratio of exhaust gas. During execution of the active control, an increasing process for increasing an intake air amount is executed. During execution of the active control, a cumulated intake air amount is calculated. A sensor detects the air-fuel ratio. It is determined whether an anomaly has occurred in the sensor during execution of the active control. A maximum execution period of a sensor diagnostic process is set to a period for the cumulated intake air amount to reach a specified threshold value. The increasing process is prohibited during the execution of the sensor diagnostic process.