Scheme 83
Function description
The airbags on both the driver and passenger sides inflate in two stages.
- A two stage inflation system, where the pressure rise in the airbag depends on the type of collision, reduces the stresses caused to the driver and/or passenger by the deployment of the airbag in comparison to a single stage system
- Each airbag has two stages (i.e. two charges each with its own igniter). The rise in pressure in the bag can be controlled by igniting the stages at an interval adapted for the particular situation
- The SRS control module calculates the retardation rate of the car at the moment of collision, enabling it to assess the type of collision within a few milliseconds
- These calculations allow the control module to determine when igniter 1 must be activated and the amount of delay before igniter 2 must be activated.
Note. Both stages are always activated during airbag deployment. The maximum pressure of the airbag will vary, depending on the type of collision.
The illustration shows the control signals. In addition to these signals there is a repetitive diagnostic signal between the SRS module and all peripheral units in the safety system. When the SRS system is started, (when the ignition is switched on), the SRS module performs a system test after which the SRS indicator lamp in the combined instrument panel goes out. The SRS module then switches to monitor mode.
The on-board diagnostic (OBD) system for the SRS continually diagnoses the function of SRS system components and stores any diagnostic trouble codes (DTCs). However, the two front seat belt buckles diagnostics are carried out by the central electronic module (CEM) which also stores any diagnostic trouble codes (DTC) for them. If the fault is registered for longer than 5 minutes, the central electronic module (CEM) transmits a diagnostic trouble code (DTC) to the SRS module. The SRS module then stores diagnostic trouble codes (DTCs) for the front seat belt buckles. The diagnostic trouble codes (DTCs) can then be read off via VIDA. The principle behind VIDA information presentation is the same as for other on-board diagnostic (OBD) systems.
System overview
See System overview
See Design
See System overview