One problem related to brake master cylinder has been reported for the 1996 GMC Sonoma. The most recently reported issues are listed below.
Abs problems; when traveling about (35-45) mph and applying the brakes, the pedal did not go down at all, and truck ran into the back of another truck. This happened on normal road conditions. Mechanic stated that the master cylinder and the power booster stopped working. GMC refuses to fix vehicle because of crash. Truck still under warranty.