Fuel cell system, fuel cell vehicle, and control method for fuel cell system

A control method for a fuel cell system used in a fuel cell vehicle, the fuel cell system including:

• a power supply circuit including a fuel cell and a secondary battery;
• an oxidant gas supply flow passage used to supply an oxidant gas to a cathode of the fuel cell;
• a pump that compresses the oxidant gas and supplies the compressed oxidant gas to the cathode, the pump being provided in the oxidant gas supply flow passage;
• and
• a control unit configured to drive the pump and dilute hydrogen retained in the cathode,
• the control method comprising stopping supplying the oxidant gas to the cathode by stopping an operation of the pump such that dilution of the hydrogen retained in the cathode is stopped, while the fuel cell vehicle remains stationary after a starter switch of the fuel cell vehicle is switched from an off state to an on state, or while a load required of the power supply circuit remains smaller than a predetermined value after the starter switch of the fuel cell vehicle is switched from the off state to the on state.