1999 Subaru Impreza Owner's Manual - Page 213

Starting and operating D When you feel the ABS system operating, you should maintain constant brake pedal pressure. Do not pump the brake pedal since doing so may defeat the operation of the ABS system. 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). B ABS system self-checking 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 started. These are caused by an automatic functional test of the ABS system being carried out and does not indicate any abnormal condition. B ABS warning light HG0346 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. - CONTINUED- 7-31