BMW 5 Series: System monitoring functions

The Advanced Crash Safety Module has the following system monitoring functions:

• System self-test (pre-drive check)
• Display of system operability
• Cyclic monitoring
• Fault display and fault storage
• Output of faults (diagnosis)
• Acoustic and visual seat belt warning
• Deactivation of the front passenger airbag and side airbag and knee airbag on the passenger's side and the knee airbag

System self test

The Advanced Crash Safety Module (ACSM) performs a system self-test after a terminal change has been made as of the "DRIVING" driving condition. The airbag indicator light is activated for roughly 5 seconds during the system self test.

Once the system self test is complete and no faults have been identified, the airbag indicator light goes out and the system is ready to operate.

Display of system operability

The airbag indicator light in the instrument panel goes out to indicate that the Advanced Crash Safety Module is ready for operation.

Cyclic monitoring

Once the system self-test has been successfully concluded and the system is ready for operation, a cyclic monitoring procedure is performed for fault monitoring purposes. This cyclical monitoring serves the internal diagnosis of the control unit and overall airbag system. Cyclical monitoring takes place continuously as of the "RESIDING" driving condition. It is only performed completely after a terminal change has been made as of the "DRIVING" driving condition.

Fault display and fault storage

The Advanced Crash Safety Module (ACSM) has a non-volatile fault memory. The airbag indicator light lights up to indicate a fault entry.

If the fault memory contains the entry that the restraint system has been activated, this only means the ignited restraint system is not available for further activation and not that it malfunctioned during the crash.

Output of faults (diagnosis)

Using the BMW diagnostic system, the fault memory can be read out via the diagnostic interface. After rectifying the faults or after renewing activated components, the fault memory can be cleared with the diagnosis command "Clear fault memory".

Acoustic and visual seat belt warning

An acoustic and visual seat belt warning is a standard feature of all vehicles equipped with the Advanced Crash Safety Module (ACSM). The Advanced Crash Safety Module (ACSM) records whether or not the driver or front passenger have fastened their seat belts. If they have not, an acoustic and visual warning is output to remind them to fasten their seatbelts. Both seat belt buckle switches are monitored separately. Depending on the national-market version, seat belt buckle switches are also installed in the rear passenger compartment and a seat belt warning is issued accordingly for the rear seat passengers.

Deactivating the passenger airbag

US vehicles

A seat occupancy mat is used on the front passenger seat for the purpose of occupancy detection and classification of occupants in the front passenger seat. A Capacitive Interior Sensing mat (CIS mat) is used in the G30.

The CIS mat is made up of 2 elements: A sensor wire, which runs parallel to the seat heating in the seat cushion and an evaluation unit. The CIS mat measures the capacity and ohmic resistance between the sensor wire (anode) and the vehicle ground (cathode) at a frequency of 120 kHz. The CIS mat determines from the change in capacity and resistance whether the front passenger seat is occupied by an adult or a child in a child seat.

The deactivation of the front passenger airbag, the side airbag and knee airbag on the passenger's side is signalled by the indicator lamp for front passenger airbag deactivation.

The indicator lamp for front passenger airbag deactivation in the roof function center lights up if a child seat with child, for e.g. a child restraint system that has been tested in accordance with the NHTSA regulations and is holding a small child, was detected on the front passenger seat or if the front passenger seat is unoccupied.

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