Supplemental restraint system (SRS), function - GF91.60-P-0002MCU
MODEL 451.3 /4
Function requirements
- Circuit 15 On
Function
The supplemental restraint system serves passive occupant safety.
The following events can be recorded and distinguished:
- Head-on collision
- Rear end collision
- Side-on collision
- Roll-over
Impact detection
The restraint systems control unit records the acceleration values using an internal sensor. The following sensors are also read in:
- Driver head/thoraxbag sensor
- Front passenger head/thoraxbag sensor
- Driver-side frontal acceleration sensor
- Passenger-side frontal acceleration sensor
Depending on the severity and nature of the impact, the following restraint equipment may be activated:
- Driver airbag unit
- Front passenger airbag unit
- Driver head/thoraxbag
- Front passenger head/thoraxbag
- Left emergency tensioning retractor
- Right emergency tensioning retractor
The emergency tensioning retractors are not activated for seat belts that are not being worn. This is monitored by the restraint systems control unit via the signals from the seat belt buckle restraint systems switches.
The occupancy of the front passenger seat is also evaluated in order to assess the situation in the vehicle interior. This is done by determining the weight on the front passenger seat by means of a pressure measurement from the seat occupied recognition pressure sensor in a seat mat filled with silicone.
The force that is introduced via the seat belt is measured by the belt tension sensor so that weight classification corrections can be made if necessary.
These two measured values are used to calculate a weight classification for the weight on the seat by the weight sensing system (WSS) control unit, which is then transmitted via CAN-B to the instrument cluster, which acts as a gateway and relays the data to the restraint systems control unit via CAN.
The following conditions are defined depending on the weight classification:
- Seat unoccupied:
the front passenger airbag unit, the front passenger head/thoraxbag and the right emergency tensioning retractor unit are shut off
- Seat occupied:
- Light weight (e.g. child seat) and belt applied: the front passenger airbag unit, the front passenger sidebag unit and the right emergency tensioning retractor unit are shut off
- Person detected:
required restraint equipment enabled
If the restraint equipment is switched off at the front passenger side, the automatic child seat recognition airbag OFF indicator lamp illuminates. Actuation takes place via the restraint systems control unit.
Frontal impact
The restraint systems control unit evaluates the data from the frontal acceleration sensors and the internal sensor in the event of a frontal impact.
Depending on the severity of the impact and the situation in the vehicle interior, the following squibs for the respective restraint systems can be triggered:
- Driver airbag ignition squib 1
- Driver airbag ignition squib 2
- Front passenger airbag squib 1
- Passenger airbag squib 2
- Left emergency tensioning retractor squib
- Right emergency tensioning retractor squib
Rear end collision
The restraint systems control unit evaluates the data from the internal sensor in the event of a rear end collision.
Depending on the severity of the impact and the situation in the vehicle interior, the following squibs for the respective restraint systems can be triggered:
- Left emergency tensioning retractor squib
- Right emergency tensioning retractor squib
Side-on collision
The restraint systems control unit evaluates information from the following components in order to detect a side-on collision:
- Sensor integrated into the restraint systems control unit
- Driver head/thoraxbag sensor
- Front passenger head/thoraxbag sensor
Depending on the severity of the impact and the situation in the vehicle interior, the following squibs for the respective restraint systems can be triggered:
- Driver head/thoraxbag squib
- Front passenger head/thoraxbag squib
- Left emergency tensioning retractor squib
- Right emergency tensioning retractor squib
Rollover along the longitudinal vehicle axis
The restraint systems control unit evaluates information from the following components in order to detect a rollover:
- Sensor integrated into the restraint systems control unit
- Driver head/thoraxbag sensor
- Front passenger head/thoraxbag sensor
Depending on the severity of the impact and the situation in the vehicle interior, the following squibs for the respective restraint systems can be triggered:
- Left emergency tensioning retractor squib
- Right emergency tensioning retractor squib
- Driver head/thoraxbag squib
- Front passenger head/thoraxbag squib
Capacitor
The supplemental restraint system is equipped with a capacitor in the restraint systems control unit.
If the battery is disconnected, then the voltage supply is assured for at least 150 ms.
System monitoring
When the ignition is switched on, the airbag indicator and warning lamp illuminates in the instrument cluster for approximately 4 s and goes off if the restraint systems control unit self-test runs successfully. If a fault occurs during the cyclic self-tests, the airbag warning lamp is permanently actuated.
As well as triggering the restraint equipment, the following interventions are controlled by the restraint systems control unit:
- Automatic engine shutoff
- Automatic emergency opening of the central locking
- Activation of hazard warning lamp function
- Switch on the interior illumination
Automatic engine shutoff
In the event of an impact the engine can be automatically shut off. The restraint systems control unit transmits the crash signal via CAN to the ME-SFI [ME] control unit, which shuts off the engine and interrupts the fuel supply via the fuel pump with fuel level sensor (M3/3).
Automatic emergency opening of the central locking
In the event of an impact the doors are automatically unlocked.
The restraint systems control unit transmits the crash signal to the SAM control unit via CAN. This actuates the following components to unlock the doors:
- Right door CL motor (M14/5)
- Left front door central locking motor (M14/6)
Activation of hazard warning lamp function
In the event of an impact the hazard warning function is automatically activated. The restraint systems control unit transmits the crash signal via CAN to the SAM control unit, which actuates the hazard warning flasher.
Switching on the interior illumination
In the event of an impact, the front interior lamp (E15/4) is automatically switched on. The restraint systems control unit transmits the crash signal via CAN to the SAM control unit, which directly actuates the interior lamp.
The interior lamp is only automatically switched on if the interior lamp switch (E15/4s1) has been pushed towards the rear.
| Supplemental restraint system (SRS), location of components | GF91.60-P-0002-01MCU | ||
| Electrical function schematic for airbag (AB), emergency tensioning retractor (ETR) | PE91.00-P-2050MCU | ||
| Wiring diagram of airbag (AB), emergency tensioning retractor (ETR) | PE91.00-P-2000MCU | ||
| Driver airbag, component description | GF91.60-P-4037MCU | ||
| Front passenger airbag, component description | GF91.60-P-4038MCU | ||
| Emergency tensioning retractor, component description | GF91.60-P-4058MCC | ||
| Head/thoraxbag, component description | GF91.60-P-4100MCU | ||
| Instrument cluster, component description | A1 | GF54.30-P-6000MCU | |
| Head/thoraxbag sensor, component description | A53, A54 | GF91.60-P-4102MCU | |
| Frontal acceleration sensor, component description | B48/1, B48/2 | GF91.60-P-4065MCU | |
| Belt tension sensor, component description | B48/3 | GF91.60-P-4108MCU | |
| Seat occupied recognition pressure sensor, component description | B48/4 | GF91.60-P-4067MCU | |
| Interior lamp, component description | E15/4 | GF82.20-P-5221MCC | |
| Restraint systems control unit, component description | N2/7 | GF91.60-P-4048MCU | |
| ME-SFI [ME] control unit, component description | N3/10 | GF07.61-P-6000MCU | |
| SAM control unit, component description | N10/10 | GF54.21-P-4157MCU | |
| Weight Sensing System (WSS) control unit, component description | N110 | GF91.60-P-4069MCU |