Q: How can you tell if you need a new power brake booster? on 1995 Chevrolet Astro

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
4.3L V-6. Has new brakes rotors drums and cylinders...Does not leak. Anti-Lock light stays on and the brake pedal will get soft and hard? Thank you!!!
(1) Answer
scan test for codes could be a bad wheel speed sensor or whoever did the brakes forgot to hook up sensor