From the user manual.
Side blind spot alert
The Side blind spot alert system detects and reports objects on either side of the vehicle, within a specified "blind spot" zone. The system alerts visually in each exterior mirror, when detecting objects that may not be visible in the interior and exterior mirrors.
Side blind spot alert uses some of the advanced parking assist sensors which are located in the front and rear bumper on both sides of the vehicle.
Side blind spot alert does not replace driver vision.
The system does not detect:
● vehicles outside the side blind zones which may be rapidly approaching
● pedestrians, cyclists or animals Before changing a lane, always check all mirrors, look over the shoulder and use the turn signal.
When the system detects a vehicle in the side blind zone while driving forward, either while passing a vehicle or being passed, an yellow
warning symbol B will illuminate in the relevant exterior mirror. If the driver then activates the turn signal, the warning symbol B starts flashing
yellow as a warning not to change lanes.
Side blind spot alert is active from speeds of 10 km/h up to 140 km/h. Driving faster than 140 km/h deactivates the system, indicated by low lighting warning symbols B in both exterior mirrors and by a message in the Driver Information Centre. Reducing the speed again will extinguish the warning symbols. If a vehicle is then detected in the blind zone, the warning symbols B will illuminate as normal on the relevant side.
When the vehicle is started, both exterior mirror displays will briefly come on to indicate that the system is operating.
The system can be activated or deactivated in the Info-Display, vehicle personalisation 3 107.
Deactivation is indicated by a message in the Driver Information Centre.
The detection zones start at the rear bumper and extend approx. three metres rearwards and to the sides. The height of the zone is approx. between half a metre and two metres off the ground. Side blind spot alert is designed to ignore stationary objects, e.g. guardrails, posts, curbs, walls and beams. Parked vehicles or oncoming vehicles are not detected.
Occasional missed alerts can occur under normal circumstances and will increase in wet conditions.
Side blind spot alert does not operate when the left or right corners of the rear bumper are covered with mud, dirt, snow, ice, slush, or in heavy rainstorms.
In the event of a fault in the system or if the system does not work due to temporary conditions, the symbols in the mirrors will be permanently
illuminated and a message is displayed in the Driver Information Centre. Seek the assistance of a workshop.