Patent attributes
An engine start is beforehand detected when a preparation operation to engine start is detected. When the preparation operation is detected based on a seat switch indicating that a driver seats himself on a driver seat, control of an electric current for a heater of an air/fuel ratio sensor is started. The air/fuel ratio sensor is then activated prior to the engine start. Failure diagnosis is conducted on a function for detecting the preparation operation. Namely, the seat switch is diagnosed as having failure, for instance, by the following. Even while a vehicle travels, the seat switch is in an OFF state indicating that no driver is seated. This structure can restrict the engine start without the air/fuel ratio sensor being pre-heated. It can also restrict deteriorating of emission.
