Fail safe

Depending on the type of fault that has occurred, the fail safe takes effect in 3 stages:

• Stage 1: substitute values

  If, for example, the steering-angle-sensor signal is unavailable, other variables are used as substitute values for the detection of cornering. The driver does not  receive a Check Control message: no fault entry.

• Stage 2: constant voltage supply

  The VDM control unit specifies a constant damping force that is the same for all 4 wheels (medium-hard damping). The damper satellites set a constant voltage supply for the EDC valves. A defective height-level sensor, for example, can be the cause. A Check Control message is output to the driver. A fault is entered in the fault memory.

• Stage 3: no voltage supply

  If a fault has occurred in activation of an EDC valve:

  The VDM control unit indicates to the damper satellites that the EDC valves may no longer be supplied with current. This causes the valve to move to a position that corresponds more to medium to harder damping. A Check Control message is output to the driver. A fault is entered in the fault memory.

Fig 1: Display - Control Message Screen

Courtesy of BMW OF NORTH AMERICA, INC.