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 signal from the lateral acceleration sensor is not available, other parameters are used as substitute values for the identification of cornering. The driver does not  receive a Check Control message: no fault entry (only a slight loss of comfort is perceptible). Any repair required is performed by fault entries from the transmitter control unit.

• Stage 2: constant voltage supply

  The EDC control unit specifies a constant damping force for all 4 wheels (medium-hard damping). A faulty vertical acceleration sensor (not M GmbH) can, for example, be the causal factor here. A Check Control message is output to the driver. A fault is entered in the fault memory (forced activation of DSC).

• Stage 3: No current supply under the following conditions:
  • If there is undervoltage on the load line (failure of fuse)
  • If there are faults on the lines to the EDC valves (short circuit to B+, short circuit to ground, line disconnection):

    The EDC control unit no longer energizes the EDC valves. 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 (forced activation of DSC).

Fig 1: Display - Control Message Screen

Courtesy of BMW OF NORTH AMERICA, INC.

Check Control message

Notes for Service department