A turn-off device for a sensor, an actuator or a control unit for a vehicle or for an industrial facility, the sensor, the actuator or the control unit being connectable via a PHY interface to a communication network, via which the sensor, the actuator or the control unit is able to exchange messages with other units of the vehicle or of the industrial facility, the turn-off device including a blocker, which physically prevents the PHY interface from sending messages to the communication network. A sensor, an actuator or a control unit that includes the turn-off device, a method for functional checking, and an associated computer program are also described.