SRS Activation

WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 2000 BMW Z3, 2000 BMW 328i, 2000 BMW 323i, 1999 BMW Z3, and 1999 BMW M3. However, it is still accessible from the selected car via links, so may be relevant.

SRS is activated when SRS control unit detects a frontal impact exceeding programmed threshold. The SRS control unit will look at the status of various sensors and deploys different parts of the SRS system as needed. Both front seat belt latches are equipped with micro-switches wired to the SRS control unit. Driver-side air bag will not be deployed by the SRS control unit if driver seat belt is buckled and impact severity is light. If vehicle is in a severe front impact the driver-side air bag will deploy whether seat belt is buckled or not.

Passenger-side front seat is equipped with a seat occupancy sensor, an analog load sensor that sends a varying signal to the Seat Occupancy Module (SBE). The SBE module converts the analog sensor input to digital output and sends it to the SRS control unit. Passenger-side air bag will be deployed in a light impact if control unit determines front passenger seat is occupied and seat belt is not buckled. In a severe front impact, air bag will deploy regardless of seat belt status. In a severe front impact, air bag will deploy even if seat is not occupied.

Seat belt contact micro-switches are also used to control emergency tensioning retractors. SRS control unit will only deploy belt tensioning retractors on belts that are buckled. In the event a front impact occurs while SRS control unit detects faults in any sensors, control unit will deploy all air bags and emergency tensioning retractors in seat belts.