A control apparatus includes an electronic control unit configured to: carry out a first diagnosis and a second diagnosis; control a first injection valve and a second injection valve such that fuel is injected from both the first injection valve and the second injection valve, and such that a fuel injection amount from the second injection valve is not reduced and a fuel injection amount from the first injection valve is reduced, when carrying out the first diagnosis; and control the first injection valve such that fuel is not injected from the first injection valve, and control the second injection valve such that the fuel injection amount from the second injection valve is reduced in a state where fuel is injected from the second injection valve, when carrying out the second diagnosis.