A brake booster system

摘要

Detecting a fault within a brake boost system of a vehicle having an inlet manifold for an engine, which provides a first source of vacuum for the brake boost system, and a second source of vacuum, preferably a super aspirator. The pressure of a brake boost chamber and the pressure of an inlet manifold for an engine of the vehicle when the secondary vacuum source is active is measured and compared to determine whether the secondary vacuum source is faulty. If the second vacuum source is faulty the use of a first auxiliary electrical and/or mechanical system which draws power from the engine is restricted so as to reduce and/or maintain the pressure of the inlet manifold. The auxiliary systems may include an alternator charging a battery and/or an air condition system. The engine power may also be restricted. The restriction is removed when it is no longer required.