Principles of Operation: Notes

The task of Advanced Crash and Safety Management is to evaluate permanently all the sensor signals in order to identify a crash situation. As a result of the sensor signals and their evaluation, the Crash Safety Module identifies the direction of the crash and the severity of the impact.

Also included is information on the occupants and whether they have their seat belts fastened or not. From this information, measures are taken to selectively trigger the necessary restraint systems.

In order to ensure ACSM operational availability at all times, the system monitors itself and indicates that it is ready for operation when the airbag warning lamp (AWL) goes out.

If a fault occurs during operation, this is stored in a fault memory, which can then be read out for diagnostic purposes.

In the event of a crash, this is communicated to the other users in the bus-system network by way of a bus telegram. The relevant control units respond to this telegram by executing their own activities.

These activities include:

• Opening the central-locking system
• Activating the hazard warning flashers
• Switching on the interior lights
• Deactivating the fuel pump
• Switching off the alternator
• Automatic emergency call

The functions of the ACSM Control unit are:

• Monitor the battery cable leading to the engine compartment for short circuits. This monitoring function is required in vehicles whose battery cable is laid directly next to the fuel line along the underbody. In the event of a short circuit, the battery cable is disconnected by the safety battery terminal.
• Seat belt reminder function, which uses optical and acoustic signals to remind the driver and front passenger to fasten their seat belts. If a child seat is to be used on the front passenger seat, the front and side airbags on the front passenger side can be deactivated by means of a key-operated switch (E85 Z4).
• Detect accident situations critical for the vehicle occupants and to activate the necessary restraint systems selectively corresponding to the crash severity. ACSM performs an internal diagnosis procedure and monitors all input and output signals.

The E64 Convertible has an additional sensor system in the Crash Safety Module for rollover detection. In the event of an imminent rollover scenario, the ROC ECU receives a signal via the K-bus to activate the rollover protection system.

Any faults are stored and indicated to the driver.