Supplemental restraint system (SRS), function - GF91.60-P-0002QA: Notes

MODEL 209.4 up to 31.5.04 

The Supplemental Restraint System (SRS) protects occupants in the front and the rear of the vehicle from injury in various types of accidents. The vehicle's SRS comprises the following airbag and emergency tensioning retractor units:

• 2-stage driver airbag with driver airbag squib 1 (R12/13) and driver airbag squib 2 (R12/14)
• 2-stage front passenger airbag with front passenger airbag squib 1 (R12/4) and front passenger airbag squib 2 (R12/5)
• Left front sidebag with left front sidebag squib (R12/20)
• Right front sidebag with right front sidebag squib (R12/21)
• Left rear sidebag with left rear sidebag squib (R12/11) (with code (293) rear left and right sidebags)
• Right rear sidebag with right rear sidebag squib (R12/12) (with code (293) rear left and right sidebags)
• Driver emergency tensioning retractor unit with driver ETR [GUS] squib (R12/1)
• Front passenger emergency tensioning retractor unit with front passenger ETR [GUS] squib (R12/2)
• Left rear emergency tensioning retractor unit with left rear ETR squib (R12/6)
• Right rear emergency tensioning retractor unit with right rear ETR squib (R12/7)

Depending on the type and severity of the accident, the airbag units and ETR units that are required to provide occupant protection are triggered by the restraint systems control unit.

The installed airbag units bear the label "SRS AIRBAG".

The restraint systems control unit (N2/7) takes into account the following input parameters:

• acceleration values of the sensors integrated into the restraint systems control unit (N2/7)
• Acceleration values for left sidebag and windowbag sensor (A53/1) and right sidebag and windowbag sensor (A54/1).

The following switch statuses are also taken into consideration for the driver seat and the front passenger seat:

• Driver side seat belt buckle restraint systems switch (S68/3)
• Passenger side seat belt buckle restraint systems switch (S68/4)
• Front passenger seat occupancy via the front passenger seat occupied and child seat recognition sensor (B48)

In the event of rear-end collisions and minor head-on collisions, only the emergency tensioning retractors are deployed; with more severe head-on collisions the front airbags are also deployed.

The corresponding sidebags are triggered if the lateral acceleration parameters of the left sidebag and windowbag sensor (A53/1) or the right sidebag and windowbag sensor (A54/1) exceed the triggering threshold if a side-on collision occurs. The front sidebags are designed to be a combination of windowbag and sidebag. When the respective airbag and emergency tensioning retractor units are deployed, the restraint systems control unit (N2/7) simultaneously issues a crash signal to the following control units:

• to the ME-SFI control unit (N3/10) for shutting down the engine. This signal is relayed via the Controller Area Network bus class B (interior) (CAN-B) to the EIS control unit (N73) and from there via the Controller Area Network bus class C (engine compartment) (CAN-C) to the ME-SFI control unit (N3/10).
• To the D2B telephone and TELE AID transmitter/receiver (A35/17) for initiating an emergency call (with code (855) TELE AID).
• To the E-call control unit (A35/8) for initiating an emergency call (with code (491) USA version, with code (498) Japan version).
• To the left door control unit (N69/1) and right door control unit (N69/2) for opening the doors in an emergency. The signal is sent to the door control units via the CAN-B.
• To the rear SAM control unit with fuse and relay module (N10/2) for activating the hazard warning system. This is switched off via the hazard warning system switch (N72/1s5).

Seat occupied recognition and automatic child seat recognition sensor 

The front passenger seat occupied and child seat recognition sensor (B48) prevents the airbag and emergency tensioning retractor units on the front passenger side from being deployed under certain conditions. The automatic child seat recognition function and the deactivation of the front passenger airbag by the seat occupied and child seat recognition sensor (B48) are indicated by the automatic child seat recognition airbag OFF indicator lamp (N72/1e1).

System monitoring 

System malfunctions are indicated by the airbag indicator and warning lamp (A1e15) and the multifunction display (A1p13) in the instrument cluster (A1). For this purpose, the instrument cluster (A1) receives the corresponding message from the restraint systems control unit (N2/7) via CAN-B.

Diagnosis 

Diagnosis takes place using the STAR Diagnosis system.

Since a "function check" is not possible for the supplemental restraint system, we will refrain here from providing a description of the individual triggering strategies. The triggering strategies are also subject to modifications, such as those resulting from new knowledge gained in the area of accident research.

Disposal 

When handling and disposing of airbag and emergency tensioning retractor units, the relevant safety and disposal information in the work instructions must be fully observed.

	Supplemental restraint system (SRS), block diagram		GF91.60-P-0002-03QA
	Rear end collision, function		GF91.60-P-2004Q
	Side impact, function		GF91.60-P-2005QA
	Head-on collision, function		GF91.60-P-2006Q