1, the sensing part of ABS speed sensor is covered by mud, soil and other pollution sources, which affects the sensor to sense the corresponding speed signal.

2. The brake system lacks necessary maintenance, the brake master cylinder has too many impurities, the seal is not tight, and the vacuum booster pump fails.

3. When the brake oil is too dirty or several brake oils are mixed and heated, there will be air resistance, oil leakage in the brake master cylinder or the sub-cylinder, and air leakage in the air storage tank or pipeline interface.