1. Start the engine, let it idle for 2-3 minutes, then turn it off.
2. Fully depress the brake pedal several times. If the pedal goes down the first time it's pressed, but gradually rises with each subsequent press, the booster is good. If the pedal height does not change, the booster is faulty.
3. With the engine off, press the brake pedal several times. While holding the pedal down, start the engine. If at the same time the pedal is slightly lowered, the amplifier is working. If the pedal position has not changed, the amplifier is faulty.
4. With the engine running, depress the brake pedal and turn off the engine. Keep the pedal depressed for 30 seconds. If the pedal height does not change, the booster is good. If the pedal rises, the amplifier is faulty.