2005 Subaru Legacy Owner's Manual - Page 394

Starting and operating The ABS system prevents the lock-up of wheels which may occur during sudden braking or braking on slippery road surfaces. This helps prevent the loss of steering control and directional stability caused by wheel lock-up. When the ABS system is operating, you may hear a chattering noise or feel a slight vibration in the brake pedal. This is normal when the ABS operates. The ABS system will not operate when the vehicle speed is below approximately 6 mph (10 km/h). ! ABS warning light ! ABS system self-check You may feel a slight shock in the brake pedal and hear the operating sound of ABS from the engine compartment just after the vehicle is started. This is caused by an automatic functional test of the ABS system being carried out and does not indicate any abnormal condition. UB7507PA The ABS warning light comes on when the ignition switch is turned to the "ON" position and goes out after about two seconds. This is an indication that the ABS system is working properly. If the warning light behaves as follows, the ABS system may not be working properly. When the warning light is on, the ABS function shuts down; however, the conventional brake system continues to operate normally. - CONTINUED - 7-39