Malfunction Threshold

The fluctuation of the brake booster pressure sensor value is less than 1 kPa (9 mmHg, 0.4 inHg) while repeating the sequence of "the vehicle speed is 0 mph (0 km/h) -> 19 mph (30 km/h) -> 0 mph (0 km/h)" for five times (it is a situation that the brake booster pressure value should drop due to the braking operations or should increase/decrease due to the negative pressure being applied from the supply source).