BRAKE-BY-WIRE BRAKING SYSTEM HAVING AT LEAST ONE BRAKE CIRCUIT, METHOD FOR OPERATING THE BRAKING SYSTEM AND DIAGNOSIS VALVE FOR A BRAKING SYSTEM OF THIS TYPE

To check the functionality/leak-tightness of a brake-by-wire brake system, a motor-operated brake pressure transducer is actuated. In this case, a pressure medium would flow out into a reservoir via a master brake cylinder. A diagnostic valve is therefore provided between the master brake cylinder and the reservoir, which diagnostic valve is composed of a check valve and a restrictor connected in parallel with respect to the check valve. The outflow of pressure medium is limited by the restrictor. Because the gradient of the pressure dissipation can be calculated, a measured pressure build-up can be compared with that which is to be expected, and a determination of functionality/leak-tightness can be derived from the comparison.