2012 Subaru Impreza Owner's Manual - Page 316

7-26 Starting and operating ABS (Anti-lock Brake 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). vehicles. . When driving on badly surfaced roads, gravel roads, icy roads, or over deep newly fallen snow, stopping distances may be longer for a vehicle with the ABS system than one without. When driving under these conditions, therefore, reduce your speed and leave ample distance from other vehicles. . 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. Electronic Brake Force Distribution (EBD) system The EBD system maximizes the effectiveness of the brakes by allowing the rear brakes to supply a greater proportion of the braking force. It functions by adjusting the distribution of braking force to the rear wheels in accordance with the vehicle's loading condition and speed. The EBD system is an integral part of the ABS system and uses some of the ABS system's components to perform its function of optimizing the distribution of braking force. If any of the ABS components used by the EBD system malfunction, the EBD system also stops working. When the EBD system is operating, you may hear a chattering noise or feel a slight vibration in the brake pedal. This is normal and does not indicate a malfunction. WARNING Always use the utmost care in driving - overconfidence because you are driving with an ABS equipped vehicle could easily lead to a serious accident. & ABS system self-check Just after the vehicle is started, you may feel on the brake pedal a vibration similar to when the ABS operates, and you may also hear the sound of the ABS working from the engine compartment. This is caused by an automatic functional test of the ABS system being carried out and does not indicate any abnormal condition. CAUTION . The ABS system does not always decrease stopping distance. You should always maintain a safe following distance from other & ABS warning light Refer to "ABS warning light" F3-18.