Snow chain detection (only BMW-approved snow chains)

It must not be possible for customers to switch active steering systems on or off! In the case of Integral Active Steering, active steering intervention on the rear axle and rear wheels is not possible with snow chains fitted. When snow chains are fitted, the rear-wheel steering is deactivated to ensure free wheel travel in all cases.

If snow chains are used, "Snow chains fitted" must be set in the control center in the settings menu. If the permitted maximum speed with snow chains of approx. 65 km/h is exceeded, the rear-wheel steering is reactivated despite the setting "Snow chains fitted"!

Snow chain detection is computed in the HSR control unit. There are two procedures for snow chain detection. Up to approx. 25 km/h, the signals of the ride height sensors (front left and rear left) are used. Up to 50 km/h, the signals of the wheel speed sensors (front left and rear left) are used. The signal shapes (pattern as the chain links move) are used to determine the presence of a snow chain. The individual signals are always combined by the HSR control unit to form one overall criterion. As a fail-safe feature, the system has recourse to the sensor signals front right and rear right.

Snow chain detection becomes active as follows:

• Terminal 15 on
• Driving speed greater than approx. 4 to 6 km/h

The snow chain detection is activated but does not compute:

• Driving speed greater than approx. 65 km/h
• No snow chain detected after a certain time

There is a Check Control message for snow chain detection.

Fig 1: Identifying Indicator Light For Active Steering

Courtesy of BMW OF NORTH AMERICA, INC.

Notes for Service department