Check the vacuum booster, its method is as follows: The engine does not start, continuously treads the brake pedal, eliminates the vacuum booster's spare power. The brake pedal is then pressed with medium pressure, so that the wheel actuator is in the braking state. Start the engine, vacuum booster in the air inlet vacuum effect into the state, such as the vacuum booster is good, should be top of the foot sense, if not, the vacuum booster is faulty. Step on the vacuum booster, in the vacuum hose place auscultation, no "AIDS, AIDS", the sound of a paragraph pinch touch, also found no leakage. If the auscultation booster has "goo, goo" gas ring, the pump inside the piston and the skin membrane and pump cavity is not sealed, so that the vacuum pump inside the servo chamber before, the posterior cavity channeling, can not produce vacuum booster effect.