164 Brakes Do not let anyone enter or exit the vehicle during the test. This will help to prevent you from mistaking pressure loss, due to air- sprung seats or the level control system, for leakage. ABS (Anti-lock Braking System) If you fail to adapt your driving style or if you are inattentive, the driving safety systems can neither reduce the risk of an accident nor override the laws of physics. Driving safety systems are merely aids designed to assist driving. You are responsi- ble for the distance to the vehicle in front, for vehicle speed and for braking in good time.
Always adapt your driving style to the prevail- ing road and weather conditions and maintain a sufficient, safe distance from other road users. Drive carefully. ABS regulates the brake pressure to prevent the wheels from locking when braking. This means that the vehicle can still be steered while braking. ABS is operational from walking pace, regard- less of road surface conditions. If the road is slippery, ABS intervenes even if you only brake gently. Important safety notes X Stop the vehicle on a level surface. X Apply the parking brake. X Use chocks to safeguard the vehicle against rolling away. Driving mode X Release the parking brake. X Turn the key to position 2 in the ignition lock.
X Call up the Reserve pressure menu win- dow in the г monitoring information menu in the on-board computer ( Y page 124). X Run the engine until the display shows a reservoir pressure of at least 16 bar. X Switch off the engine. X Turn the key to the drive position in the ignition lock. X Call up the Reserve pressure menu win- dow in the г monitoring information menu in the on-board computer once again ( Y page 124). G WARNING If ABS is malfunctioning, the wheels could lock when braking. The steerability and brak- ing characteristics are thus severely impaired. There is an increased risk of skidding and an accident. Drive on carefully.
Have the ABS checked at a qualified specialist workshop as soon as pos- sible. X Depress the brake pedal and keep it in this position. X Read off the reservoir pressure after approximately 1 minute. X Read off the reservoir pressure again after another minute. If no significant loss of pressure can be detected in the Reserve pressure menu window in the on-board computer after this minute, the compressed-air brake system is free from leaks. If a significant loss of pressure is detected, the compressed-air brake system is leak- ing. i The tyre pressure table can be found in the "Technical data" section ( Y page 342). ABS only functions properly if you use wheels with the specified tyre size.
The full effect of the ABS system is only ach- ieved when the tyre pressure is set correctly and adjusted to the load. In wintry driving conditions, always use winter tyres (M+S tyres), if necessary with snow chains. When the front-axle differential lock is engaged, ABS is deactivated. X If the compressed-air brake system is leak- ing, have it checked and repaired at a quali- fied specialist workshop.