One problem related to air brake wheel speed sensor has been reported for the 2001 GMC Safari. The most recently reported issues are listed below.
Abs left wheel speed sensor failed @30k miles,then the right 300 miles later. With no warning and no warning light the car would slow to about 15mph then the brake pedal will go to the floor and car would not stop. Now 500 miles later same problem but the dealer is saying speed sensors were dirty !.