Normal Operation and Fault Conditions

Through the use of the brake booster vacuum sensor, the ABS module monitors the vacuum in the brake booster. When the vacuum reaches the low side of a predetermined threshold, the ABS module provides a ground for the vacuum pump relay coil to activate the brake vacuum pump. Once the vacuum in the brake booster reaches the high side of a predetermined threshold, the ABS module removes the ground connection for the vacuum pump relay coil, deactivating the brake vacuum pump. 

A leak in the brake booster vacuum system, an inoperative relay, an inoperative pump, a short to ground, a short to voltage or an open in the vacuum pump relay or vacuum pump motor circuits can cause the ABS module to set one or more DTCs.