Abstract: The present invention provides a malfunction diagnosing apparatus for an engine which enables selection of a fuel to be supplied to a tank from fuels having different properties. The apparatus includes a determining unit determining whether fuel has been supplied to the tank, a sensor detecting a property of the fuel supplied from the tank to an injection valve, an air-fuel ratio control unit determining an air-fuel ratio correction amount according to a difference between a target air-fuel ratio and an actual air-fuel ratio and according to the property of the fuel sensed by the sensor to correct a fuel injection quantity using the air-fuel ratio correction amount, and a diagnosing unit that definitively diagnoses malfunctions of the determining unit, the sensor, and a fuel system, based on a combination of a determination by the determining unit, detection by the sensor, and the air-fuel ratio correction amount or the difference.

Abstract: The present invention provides a malfunction diagnosing apparatus for an engine which enables selection of a fuel to be supplied to a tank from fuels having different properties. The apparatus includes a determining unit determining whether fuel has been supplied to the tank, a sensor detecting a property of the fuel supplied from the tank to an injection valve, an air-fuel ratio control unit determining an air-fuel ratio correction amount according to a difference between a target air-fuel ratio and an actual air-fuel ratio and according to the property of the fuel sensed by the sensor to correct a fuel injection quantity using the air-fuel ratio correction amount, and a diagnosing unit that definitively diagnoses malfunctions of the determining unit, the sensor, and a fuel system, based on a combination of a determination by the determining unit, detection by the sensor, and the air-fuel ratio correction amount or the difference.