Active main beam

Active main beam is a function which uses a camera sensor at the top edge of the windscreen to detect the headlamp beams from oncoming traffic or the rear lights of vehicles in front, and then switches from main beam to dipped beam.
P5-1617 Stalk with turning ring in AHBC position
The symbol P5-1507 Symbol AHBC activated represents active main beam.

The function can start while driving in the dark when the car's speed is approx. 20 km/h (approx. 12 mph) or higher. The function can also take streetlights into account. When the camera sensor no longer detects any oncoming car or car in front, main beam is switched on again after about a second.

Activate active main beam

Active main beam is activated and deactivated by turning the rotating ring on the right-hand stalk switch to position P5-1507 Symbol AHBC activated. The rotating ring then returns to position P5-1707 Symbol AUTO. When active main beam is activated, the symbol P5-1507 Symbol AHBC activated illuminates with a white glow in the driver display. When main beam is activated, the symbol shines blue.

If active main beam is deactivated while main beam is on, the lighting is immediately reset to dipped beam.

Adaptive functionality

For cars with LED1 headlamps*, active main beam has adaptive functionality2. In this case, unlike what happens during conventional dimming, the light beam continues to illuminate with main beam on both sides of oncoming traffic or vehicles ahead – only the part of the light beam that points directly to the vehicle is dimmed.

P5-1507 Principle AHBC2
Adaptive functionality: Dipped beam directly towards oncoming vehicle, but continued main beam on both sides of the vehicle.

The main beam is partly dimmed, i.e. if the light beam shines with slightly more than dipped beam, the symbol P5-1507 Symbol AHBC activated in the driver display shines blue.

Limitations for active main beam

The camera sensor on which the function is based has limitations.

P5-1519 Symbol Active HeadBeamTempUnavailable

If this symbol is shown in the driver display, together with the message Active High Beam Temporarily unavailable, then switching between main and dipped beam must be performed manually. The P5-1507 Symbol AHBC activated symbol extinguishes when these message are shown.

P5-1519 Symbol FactoryMode_104

The same applies if this symbol is shown together with the message Windscreen sensor Sensor blocked, see Owner's manual.

Active main beam may be temporarily unavailable e.g. in situations with dense fog or heavy rain. When active main beam becomes available again, or the windscreen sensors are no longer blocked, the message goes out and the P5-1507 Symbol AHBC activated symbol illuminates.


Active main beam is an aid for using the optimum beam pattern when conditions are favourable.

The driver always bears responsibility for manually switching between main and dipped beam when traffic situations or weather conditions so require.

  1. 1 LED (Light Emitting Diode)
  2. * Option/accessory.
  3. 2 Depending on the car's equipment level.