Actuate Supplemental Restraint System, Function - GF91.60-P-2012GWM

Model 463 (except 463.342)

as of model year 2019

Function requirements, general

Circuit 15R ON

The electronic ignition lock control unit (N73) sends the circuit 15 status via the user interface CAN (CAN HMI) to the supplemental restraint system control unit (N2/10).

Actuate Supplemental Restraint System, general

The supplemental restraint system monitors the occupancy of the front passenger seat and the status of the seat belts (fastened or not fastened) and adapts its triggering behavior on the basis of this information.

The supplemental restraint system deployment function includes the following subfunctions:

Function sequence system monitoring
Function sequence for evaluation of occupation status on front passenger seat
Function sequence for detecting status of seat belts
Function sequence for impact detection
Function sequence for frontal impact
Function sequence in the event of a side impact
Function sequence for rear impact
Function sequence for rollover
Function sequence for additional functions in the event of a crash

Function sequence system monitoring

When circuit 15R is switched on, the following indicator lamps are actuated:

Supplemental Restraint System indicator lamp in the instrument cluster (A1)
Front passenger airbag ON indicator lamp (N72/1e3)
Front passenger airbag OFF indicator lamp (N72/1e4)

Following a successful self-test (4 s) the indicator lamp for the Supplemental Restraint System is switched off. The status of the front passenger airbag is displayed via the front passenger airbag ON indicator lamp or via the front passenger airbag OFF indicator lamp. The supplemental restraint system control unit sends the request to switch on the supplemental restraint system indicator lamp via user interface CAN to the instrument cluster. The supplemental restraint system control unit sends the request to switch on the respective front passenger airbag indicator lamp via user interface CAN, head unit (A26/17), telematics CAN (CAN A), Audio/COMAND control panel A40/9) and LCP LIN (LIN A3) to the upper control panel control unit N72/1, which directly actuates the corresponding front passenger airbag indicator lamp.

The Supplemental Restraint System control unit continues to monitor the Supplemental Restraint System while driving and notifies the driver of any errors on the display and with the Supplemental Restraint System indicator lamp in the instrument cluster. The supplemental restraint system control unit transmits the request to display a corresponding message via user interface CAN to the instrument cluster The faults are stored in the nonvolatile memory of the supplemental restraint system control unit.

Function sequence for evaluation of occupation status on front passenger seat

The deployment behavior of the restraint equipment on the front passenger side is adapted based on the occupancy status of the front passenger seat.

Function sequence for detecting status of seat belts

The deployment behavior of the restraint equipment is adapted based on the status of the seat belts (fastened or unfastened). The status of each seat belt is defined by the corresponding seat belt buckle switch:

Driver seat belt buckle switch (S68/3)
Front passenger seat belt buckle switch (S68/4)
Left rear seat belt buckle switch (S68/11)
Right rear belt buckle switch (S68/12)

The supplemental restraint system control unit reads in the status of the driver belt buckle switch and the status of the front passenger belt buckle switch directly.

The rear SAM control unit (N10/8) reads in the status of the rear seat belt buckle switch directly and transmits this via the interior CAN (CAN B), the electronic ignition lock control unit and the user interface CAN to the Supplemental Restraint System control unit.

The status of the center rear belt buckle switch (S68/14) does not have any influence on triggering behavior of the supplemental restraint system.

Function sequence for impact detection

The SRS control unit distinguishes between the following events:

Frontal impact
Side impact
Rear impact
Rollover (along vehicle's longitudinal axis)

To do so, the signals of the following sensors are evaluated:

Integrated sensors
Left sidebag sensor (A53)
Right sidebag sensor (A54)
Left frontal acceleration sensor (B48/1)
Right frontal acceleration sensor (B48/2)
Left front door pressure sensor (B48/7)
Right front door pressure sensor (B48/8)
Left rear door pressure sensor (B48/9) (with code SH1 (Sidebags in rear bench seat))
Right rear door pressure sensor (B48/10) (with code SH1 (Sidebags in rear bench seat))

The sensor signals are read in directly by the supplemental restraint system control unit.

The lateral acceleration of the vehicle is also evaluated. It is detected by the acceleration sensor integrated into the supplemental restraint system control unit.

The traffic area in front of the vehicle is monitored by radar-assisted evaluation of the surroundings. This makes it possible to detect an imminent collision at an early stage. The respective deployment points are adapted in accordance with the situation.

Function sequence for frontal impact

The deployment of the restraint equipment takes place depending the severity of the impact, the occupation of the front passenger se and the status of the seat belts. The following squibs can be ignited (maximum):

Driver emergency tensioning retractor squib (R12/1)
Front passenger emergency tensioning retractor squib (R12/2)
Front passenger airbag squib 1 (R12/4)
Front passenger airbag squib 2 (R12/5)
Left rear emergency tensioning retractor squib (R12/6)
Right rear emergency tensioning retractor squib (R12/7)
Driver airbag squib 1 (R12/13)
Driver airbag squib 2 (R12/14)
Front passenger kneebag squib (R12/24)
Driver kneebag squib (R12/25)
Front passenger belt force limiter (R12/26) (with code ZU7 (National version for Canada) or code ZU8 (National version for USA))
Driver belt force limiter (R12/27) (with code ZU7 (National version for Canada) or code ZU8 (National version for the USA))
Driver anchor fitting tensioner squib (R12/37)
Front passenger anchor fitting tensioner squib (R12/38)
Inerting system squib (R12/69) (with code Y65 (Alternative _ refrigerant) and gasoline engine)

If the inerting system squib is deployed, Argon inert gas flows out of the gas cylinder into the engine compartment. This displaces the atmospheric oxygen in areas close to the engine that present a fire hazard This prevents the risk of fire caused by refrigerant flowing out of the air conditioning system.

The squibs are actuated directly by the supplemental restraint system control unit.

The following situations are taken into account:

Position of the driver's seat (with code ZU7 (National version for Canada) or code ZU8 (National version for USA)):
The supplemental restraint system control unit uses the status of the driver seat position detection switch (S68/19) to decide about the corresponding trigger time of the driver airbag. The supplemental restraint system control unit reads in the status of the driver seat position detection switch directly.
Position of the front passenger seat (with code ZU7 (National version for Canada) or code ZU8 (National version for USA)): The supplemental restraint system control unit uses the status of the front passenger seat position detection switch (S68/20) to decide about the corresponding trigger time of the front passenger airbag. However, this only applies if an occupied front passenger seat has been detected. The supplemental restraint system control unit reads in the status of the front passenger seat position detection switch directly.
Occupancy status of the front passenger seat:
- If the front passenger seat is unoccupied or occupied with a child seat and the seat belt has not been fastened, no restraint equipment is triggered at the front passenger side.
- If the front passenger seat is unoccupied or occupied with a child seat and the seat belt has been fastened, the front passenger airbag is not triggered.
- If the front passenger seat is occupied by a person and the seat belt is not fastened, only the front passenger airbag is triggered at the front passenger side.
Driver seat belt buckle status:
If the seat belt is not fastened, the seat belt tensioner, the anchor fitting tensioner and the seat belt force limiter (with code ZU7 (National version for Canada) or code ZU8 (National version for USA)) are not triggered on the driver's side.
Status of seat belt buckles in rear:

No restraint equipment is triggered if the seat belt is not fastened.

Function sequence in the event of a side impact

The deployment of the restraint equipment takes place depending on the severity of the impact, the occupation of the front passenger seat and the status of the seat belts.

The following squibs can be ignited (maximum):

Driver ETR [GUS] squib
Front passenger ETR [GUS] squib
Left rear emergency tensioning retractor squib
Right rear emergency tensioning retractor squib
Driver sidebag squib (R12/9)
Front passenger sidebag squib (R12/10)
Squib side airbag in rear at left (R12/11) (with code SH1 (Sidebags in rear bench seat))
Squib side airbag in rear at right (R12/12) (with code SH1 (Sidebags in rear bench seat))
Left windowbag squib (R12/22)
Right windowbag squib (R12/23)

The squibs are actuated directly by the supplemental restraint system control unit.

The following situations are taken into account:

Occupancy status of the front passenger seat:
- If the front passenger seat is unoccupied and the seat belt has not been fastened, the emergency tensioning retractor and the sidebag are not triggered at the front passenger side.
- If the front passenger seat is occupied (person or child seat) and the seat belt has not been fastened the emergency tensioning retractor is not triggered at the front passenger side.
Driver seat belt buckle status:
If the seat belt is not fastened, emergency tensioning retractor is not triggered at the driver side.
Status of seat belt buckles in rear:

If the seat belt is not fastened, the respective emergency tensioning retractor in the rear is not triggered.

Function sequence for rear impact

The deployment of the restraint equipment takes place depending on the severity of the impact and the status of the seat belts. The following squibs can be ignited (maximum):

Driver ETR [GUS] squib
Front passenger ETR [GUS] squib
Left rear emergency tensioning retractor squib
Right rear emergency tensioning retractor squib
Driver-side anchor fitting tensioner squib
Front passenger anchor fitting tensioner squib

The squibs are actuated directly by the supplemental restraint system control unit.

The following situations are taken into account:

Driver/front passenger seat belt buckle status:
No restraint equipment is triggered if the seat belt is not fastened.
Status of seat belt buckles in rear:

No restraint equipment is triggered if the seat belt is not fastened.

Function sequence for rollover

The deployment of restraint equipment takes place depending on the status of the seat belts.

The following squibs can be ignited (maximum):

Driver ETR [GUS] squib
Front passenger ETR [GUS] squib
Left rear emergency tensioning retractor squib
Right rear emergency tensioning retractor squib
Left windowbag squib
Right windowbag squib
Driver-side anchor fitting tensioner squib
Front passenger anchor fitting tensioner squib

The squibs are actuated directly by the supplemental restraint system control unit.

The following situations are taken into account:

Driver/front passenger seat belt buckle status:
If the seat belt is not fastened, the seat belt tensioner and the anchor fitting tensioner are not triggered.
Status of seat belt buckles in rear:

If the seat belt is not fastened, the respective emergency tensioning retractor in the rear is not triggered.

Function sequence for additional functions in the event of a crash

The additional functions in the event of a crash include the following subfunctions:

Function sequence for activating the hazard warning flasher function
Function sequence for switching on interior illumination
Function sequence for opening the central locking system
Function sequence for opening the side windows
Function sequence for shutting off the engine
Function sequence for switching off the A/C
Function sequence for triggering the battery clamp electrical fuse (F108)
Function sequence for shutting off the stationary heater (with code H12 (Stationary heater))
Function sequence for automatic emergency call (with code EK0 (Mercedes-Benz Emergency Call System))
Function sequence for activating crash-active exit aid

Function sequence for activating the hazard warning flasher function

The hazard warning flasher function is activated automatically in order to warn other road users in the event of an accident. The supplemental restraint system control unit transmits the crash signal via the user interface CAN, the electronic ignition lock control unit and the interior CAN to the front SAM control unit (N10/6). The front SAM control unit then activates the hazard warning flasher function.

The crash signal is also transmitted via a direct line from the supplemental restraint system control unit to the front SAM control unit. The front SAM control unit then generates a redundant crash signal on the interior CAN.

Function sequence for switching on interior illumination

In order to make it easier for the vehicle occupants or persons giving assistance to orientate themselves inside the vehicle in the event of an accident, the interior illumination is automatically activated. The supplemental restraint system control unit transmits the crash signal via the user interface CAN, the electronic ignition lock control unit and the interior CAN to the front SAM control unit. The front SAM control unit then activates the interior illumination.

Function sequence for opening the central locking system

After an accident, all doors, the trunk lid or the liftgate and the tank cap are automatically unlocked via the central locking The unlocking of the doors allows rescuers to gain access to any vehicle occupants who may be injured. The unlocking of the rear-end door enables access to aids such as the warning triangle and first-aid kit (hard case). The unlocking of the tank cap enables access to the QR code located in the tank cap with which the rescue services can quickly determine the relevant rescue card for the vehicle.

The supplemental restraint system control unit transmits the crash signal via the user interface CAN, the electronic ignition lock control unit and the interior CAN to the following control units:

Rear SAM control unit
Left front door control unit (N69/1)
Right front door control unit (N69/2)
Left rear door control unit (N69/3)
Right rear door control unit (N69/4)

The central locking system is unlocked after a waiting time of 10 s. In the event of a rear-end collision, the central locking is immediately unlocked.

Function sequence for opening the side windows

Smoke particles are produced in the vehicle interior when the pyrotechnical restraint equipment is triggered. The side windows at front are automatically opened a gap by the power window lifters in order to achieve quick dispersion of these smoke particles. The supplemental restraint system control unit transmits the crash signal via the user interface CAN, the electronic ignition lock control unit and the interior CAN to the following control units:

Left front door control unit
Right front door control unit

The front door control units implement this request and the side windows are opened.

Function sequence for shutting off the engine

After an accident, the engine is automatically switched off and the fuel supply stopped to reduce the risk of fire. The Supplemental Restraint System control unit transmits the crash signal via the user interface CAN, the electronic ignition lock control unit, the chassis FlexRay (Flex E), the powertrain control unit (N127) and the engine CAN (CAN C) to the CDI control unit (N3/9) (diesel engine) or to the ME-SFI [ME] control unit (N3/10) (gasoline engine). This then causes the engine to be shut off and the fuel supply to be stopped.

The crash signal is also transmitted via a direct line by the supplemental restraint system control unit to the CDI control unit or to the ME-SFI [ME] control unit.

Function sequence for switching off the A/C

In order to prevent hazardous gases from entering the vehicle interior after an accident, the climate control control unit (N22/1) switches off the air conditioning is and closes the air recirculation flap. The Supplemental Restraint System control unit transits the crash signal via the user interface CAN, the electronic ignition lock control unit and the interior CAN to the climate control control unit, which implements this request.

Function sequence for triggering the battery clamp electrical fuse

In order to reduce the risk of fire after an accident, the battery line is disconnected from the on-board electrical system by triggering the battery clamp electrical fuse.

The battery line is designed as a bus bar with a predetermined fracture point (3) in the housing. After a corresponding crash event has occurred, the battery clamp electrical fuse is directly actuated by the SRS control unit. Because of the actuation, pressure builds up in the chamber (1). The piston (2) then moves against the predetermined fracture point, thereby disconnecting the bus bar. Time sequence:

After 300 μs the piston movement is started. ***
Bus bar disconnection is finished after 450 μs. By triggering the pyrofuse, the starter (M1), alternator (G2) and engine compartment prefuse box (F32/3) are disconnected from the on-board electrical system.

Courtesy of MERCEDES-BENZ USA

Function sequence for shutting off the stationary heater (with code H12 (Stationary heater))

In order to reduce the risk of fire following an accident, the stationary heater is automatically switched off. The Supplemental Restraint System control unit transmits the crash signal via the user interface CAN, the electronic ignition lock control unit, the interior CAN, the climate control control unit and climate control LIN 2 (LIN B8-2) to the stationary heater control unit (A6n1). The stationary heater is then switched off permanently.

Function sequence for automatic emergency call (with code EK0 (Mercedes-Benz Emergency Call System))

An emergency call is made automatically after an accident. Depending on the type of transmission involved the following data, among others, are sent to the Mercedes-Benz Emergency Call Center:

GPS position data for the vehicle
Last known GPS position data for vehicle route
Direction of travel
Vehicle identification number
Estimated accident severity
Estimated number of people in vehicle
Type of drive in vehicle

Function sequence for activating crash-active exit aid

To make it easier for the driver to exit the vehicle or for first aiders to remove the driver from the vehicle after an accident, following a crash event the steering column is automatically adjusted upward to a predefined position if the following occurs:

Driver door opened
Change of circuit status from circuit 15C On to circuit 15C Off

The supplemental restraint system control unit transmits the crash signal via the user interface CAN, the electronic ignition lock control unit and the interior CAN to the driver seat control unit (N32/1), which controls the crash-active easy exit function.

	Electric function schematic for deployment of supplemental restraint system		PE91.60-P-2055-97ZGB
	Overview of system components for supplemental restraint system		GF91.60-P-9996GWM