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

Model 205, 253 

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 deployment behavior on the basis of this information.

The supplemental restraint system deployment function includes the following functions:

• System monitoring 
• Evaluation of occupancy status of front passenger seat 
• Detection of seat belt status 
• Impact detection 
• Frontal impact deployment 
• Side impact deployment 
• Rear end collision deployment 
• Rollover deployment 
• Additional functions in event of a crash 

System monitoring 

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

• Supplemental restraint system indicator lamp (A1e15) in the instrument cluster (A1)
• Front passenger airbag OFF indicator lamp (N72/1e1) (with code U10 (Automatic front passenger airbag shutoff))
• Front passenger airbag ON indicator lamp (N72/1e2) (with CODE U10 (Automatic front passenger airbag deactivation))

Following a successful self-test (4 s) the indicator lamp for the Supplemental Restraint System is switched off. On vehicles with CODE U10 (Automatic front passenger airbag deactivation) the front passenger airbag ON indicator lamp or the front passenger airbag OFF indicator lamp indicates the corresponding occupancy status of the front passenger seat.

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.

Model 205 up to model year 2019, model 205 as of model year 2019 except code 446 (Touchpad only), model 253 (except for 253.99): 

The Supplemental Restraint System control unit sends the request to switch on the respective front passenger airbag indicator lamp over the user interface CAN, head unit (A26/17), telematics CAN (CAN A), Audio/COMAND control panel (A40/9) and the LCP-LIN (LIN A3) to the upper control panel control unit (N72/1).

Model 205 as of model year 2019 with code 446 (Touchpad only), model 253.99 with code 446 (Touchpad only): 

The Supplemental Restraint System control unit sends the request to switch on the respective front passenger airbag indicator lamp over the user interface CAN, head unit, telematics CAN, touchpad (A105) and the LCP-LIN to the upper control panel control unit.

The upper control panel control unit directly actuates the corresponding front passenger airbag indicator lamp. When driving, the Supplemental Restraint System control unit continues to constantly monitor the Supplemental Restraint System. The driver is notified of any faults on the multifunction display (A1p13) and by 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.

Evaluation of occupancy status of front passenger seat 

The deployment behavior of the restraint equipment at the passenger-side is matched to the occupancy status of the front passenger seat.

Model 205, 253

except code U10 (Automatic seat occupancy recognition and child seat recognition)

The status of the seat occupied recognition does not have any influence on the deployment behavior of the supplemental restraint system.

Detection of seat belt status 

The deployment behavior of the restraint equipment is adapted on basis of the status of the seat belts (worn or not being worn). The status of the respective seat belt is defined by the corresponding 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)
• Center rear seat belt buckle switch (S68/14) (model 205.0/1/2, 253)

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.

Model 205.0/1/2, 253

The status of the center rear belt buckle switch does not have any influence on deployment behavior of the supplemental restraint system.

Impact detection 

The supplemental restraint system control unit makes a distinction between a:

• 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) (model 205.0/1/2, 253 with CODE 298 (Sidebag in rear including belt force limiter))
• Right rear door pressure sensor (B48/10) (model 205.0/1/2, 253 with CODE 298 (Sidebag in rear including belt force limiter))

The supplemental restraint system control unit directly reads in the sensor signals.

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

Model 205, 253

with code 239 (DISTRONIC PLUS)

Model 205, 253

with code 23P (Driving Assistance package)

Model 205, 253

with code 258 (COLLISION PREVENTION ASSIST)

The traffic area in front of the vehicle is monitored via the radar-supported assessment 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. On vehicles with code 23P (Driving Assistance package), the traffic area behind the vehicle is also monitored.

Frontal impact deployment 

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 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) (model 205.3/4 with CODE 494 (USA version) or CODE 460 (Canada version))
• Driver kneebag squib (R12/25)
• Front passenger belt force limiter (R12/26) (with CODE 494 (USA version) or CODE 460 (Canada version))
• Driver belt force limiter (R12/27) (with CODE 494 (USA version) or CODE 460 (Canada version))
• Driver anchor fitting tensioner squib (R12/37) (with CODE 494 (USA version) or CODE 460 (Canada version))
• Front passenger anchor fitting tensioner squib (R12/38) (with CODE 494 (USA version) or CODE 460 (Canada version))
• Front passenger airbag ventilation valve squib (R12/44) (with CODE 494 (USA version) or CODE 460 (Canada version))

The supplemental restraint system control unit directly actuates the squibs.

The following situations are taken into account:

• Position of the driver seat (with CODE 494 (USA version) or CODE 460 (Canada version)):

The Supplemental Restraint System control unit uses the status of the driver seat position detection switch (S68/19) to determine the corresponding driver airbag deployment time. 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 494 (USA version) or CODE 460 (Canada version)):

The Supplemental Restraint System control unit uses the status of the front-passenger seat position detection switch (S68/20) to determine the corresponding front passenger airbag deployment time. 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 belt lock tongue has not been inserted, no restraint equipment is triggered at the passenger side.
• If the front passenger seat is unoccupied or occupied with a child seat and the belt lock tongue has been inserted, the front passenger airbag is not triggered.
• If the front passenger seat is occupied by a person and the belt tab has not been inserted, the emergency tensioning retractor, the anchor fitting tensioner (with CODE 494 (USA version) or CODE 460 (Canada version)) and the belt force limiter (with CODE 494 (USA version) or CODE 460 (Canada version)) are not deployed on the front passenger side.
• Driver seat belt buckle status:

If the belt tab is not inserted, the emergency tensioning retractor, the anchor fitting tensioner (with CODE 494 (USA version) or CODE 460 (Canada version)) and the belt force limiter (with CODE 494 (USA version) or CODE 460 (Canada version) on the driver side are not deployed.

• Status of seat belt buckles in rear:

If the belt lock tongue is not inserted, the relevant emergency tensioning retractor in the rear is not triggered.

Side impact deployment 

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)
• Left rear sidebag squib (R12/11) (with CODE 298 (Rear sidebag including belt force limiter))
• Right rear sidebag squib (R12/12) (with CODE 298 (Rear sidebag including belt force limiter))
• Left windowbag squib (R12/22) (model 205.0/1/2/3, 253)
• Right windowbag squib (R12/23) (model 205.0/1/2/3, 253)
• Driver anchor fitting tensioner squib (with CODE 494 (USA version) or CODE 460 (Canada version))
• Front passenger anchor fitting tensioner squib (with CODE 494 (USA version) or CODE 460 (Canada version))
• Left headbag squib (R12/39) (model 205.4)
• Right headbag squib (R12/40) (model 205.4)

The supplemental restraint system control unit directly actuates the squibs.

The following situations are taken into account:

• Occupancy status of the front passenger seat:
  • If the front passenger seat is unoccupied and the belt tab has not been inserted, the emergency tensioning retractor, the anchor fitting tensioner (with CODE 494 (USA version) or CODE 460 (Canada version)) and the sidebag are not deployed on the passenger side.
  • If the front passenger seat is occupied (person or child seat) and the belt tab has not been inserted, the emergency tensioning retractor and the anchor fitting tensioner (with CODE 494 (USA version) or CODE 460 (Canada version)) are not deployed on the passenger side.
• Driver seat belt buckle status:

  If the belt tab is not inserted, the emergency tensioning retractor and anchor fitting tensioner (with CODE 494 (USA version) or CODE 460 (Canada version)) on the driver side are not deployed.

• Status of seat belt buckles in rear:

If the belt lock tongue is not inserted, the relevant emergency tensioning retractor in the rear is not triggered.

Rear end collision deployment 

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 anchor fitting tensioner squib (with CODE 494 (USA version) or CODE 460 (Canada version))
• Front passenger anchor fitting tensioner squib (with CODE 494 (USA version) or CODE 460 (Canada version))

The supplemental restraint system control unit directly actuates the squibs.

The following situations are taken into account:

• Driver/front passenger seat belt buckle status:

  If the belt tab is not inserted, the corresponding emergency tensioning retractor and anchor fitting tensioner (with CODE 494 (USA version) or CODE 460 (Canada version)) are not triggered.

• Status of seat belt buckles in rear:

If the belt lock tongue is not inserted, the relevant emergency tensioning retractor in the rear is not triggered.

Rollover deployment 

Restraint equipment is deployed 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 (model 205.0/1/2/3, 253)
• Right windowbag squib (model 205.0/1/2/3, 253)
• Driver anchor fitting tensioner squib (with CODE 494 (USA version) or CODE 460 (Canada version))
• Front passenger anchor fitting tensioner squib (with CODE 494 (USA version) or CODE 460 (Canada version))
• Left headbag squib (model 205.4)
• Right headbag squib (model 205.4)
• Left roll bar squib (R12/61) (model 205.4)
• Right roll bar squib (R12/62) (model 205.4)

The supplemental restraint system control unit directly actuates the squibs.

The following situations are taken into account:

• Driver/front passenger seat belt buckle status:

If the belt tab is not inserted, the corresponding emergency tensioning retractor and anchor fitting tensioner (with CODE 494 (USA version) or CODE 460 (Canada version)) are not triggered.

• Status of seat belt buckles in rear:

If the belt lock tongue is not inserted, the relevant emergency tensioning retractor in the rear is not triggered.

Additional functions in event of a crash 

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

• Switching off the engine (except model 253.99) 
• Triggering of inerting system (with code 2U8 (Alternative refrigerant) and engine 177, 264, 274, 276) 
• Triggering of pyrotechnical separator (K88) (model 205.012/013/047/147/212/213/247, 253.354/954) 
• Deactivation of high-voltage components (model 205.012/013/047/147/212/213/247, 253.354/954/992) 
• Deactivation of A/C system 
• Deactivation of stationary heater (with code 228 (Stationary heater)) 
• Automatic emergency call (model 205 with code 347 (Mercedes-Benz emergency call system) or code 348 (Emergency call/assist system) or code 350 (eCall Europe emergency call system) or code 351 (Emergency call system (HERMES)) or code 360 (HERMES UMTS) or code 362 (HERMES LTE)) 
• Activation of hazard warning flasher function 
• Switching on interior lights 
• Unlock central locking 
• Opening of side windows 
• Activation of crash-active easy exit feature (with code 275 (Memory package)) 

Switching off the engine (except model 253.99) 

In order to reduce the risk of fire after an accident, the engine is automatically shut off and the fuel supply shut-off. The supplemental restraint system control unit sends the crash signal via the user interface CAN, electronic ignition lock control unit, chassis FlexRay, powertrain control unit (N127), and 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.

Triggering of inerting system (with code 2U8 (Alternative refrigerant) and engine 177, 264, 274, 276) 

The inerting system prevents any leaking refrigerant from the A/C system igniting on hot parts of the engine.

If the Supplemental Restraint System control unit detects a frontal impact, it actuates the inertization system squib (R12/69). 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.

Triggering of pyrotechnical separator (model 205.012/013/047/147/212/213/247, 253.354/954) 

To reduce the fire hazard after an accident, the battery line is disconnected from the on-board electrical system by triggering the pyrotechnical separator.

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 pyrotechnical separator is directly actuated by the supplemental restraint system control unit. Because of the actuation, pressure builds up in the chamber (1). The piston (2) then moves up against the predetermined fracture point (3), thereby disconnecting the bus bar.

Time sequence:

After 300 μs the piston movement is started.

Bus bar disconnection is finished after 450 μs.

Courtesy of MERCEDES-BENZ USA

Deactivation of high-voltage components (model 205.012/013/047/147/212/213/247, 253.354/954/992) 

In order to reduce the risk of fire after an accident, the high-voltage components are 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 chassis FlexRay, the powertrain CAN and the hybrid CAN (CAN L) to the battery management system control unit (N82/2). It switches the high-voltage components off.

Redundantly to this, the control terminal line (circuit 30c) is interrupted by the triggering of the pyrofuse (F63). The voltage drop on the high-voltage components causes the high voltage on-board electrical system to be shutoff. The supplemental restraint system control unit directly actuates the pyrofuse.

Deactivation of A/C system 

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 transmits 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.

Deactivation of stationary heater (with code 228 (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 and the interior CAN to the A/C control unit. When the stationary heater is activated, the climate control control unit activates the stationary heater emergency shutoff. To do so, it sends the heat request (0 %) over the air conditioning control LIN 2 (LIN B8-2) to the stationary heater control unit (A6n1). The stationary heater is then switched off permanently.

Automatic emergency call (model 205 with code 347 (Mercedes-Benz emergency call system) or code 348 (Emergency call/assist system) or code 350 (eCall Europe emergency call system) or code 351 (Emergency call system (HERMES)) or code 360 (HERMES UMTS) or code 362 (HERMES LTE)) 

An emergency call is made automatically after an accident. The Supplemental Restraint System control unit sends the crash signal over the following connections, depending on the vehicle equipment involved:

• Over the user interface CAN to the head unit (with code 347 (Mercedes-Benz emergency call system))
• Over the user interface CAN, electronic ignition lock control unit and the diagnostics CAN (CAN D) to the telematics services communication module (N112/1) (with code 350 (eCall Europe emergency call system))
• Over the user interface CAN, electronic ignition lock control unit and the diagnostics CAN to the HERMES control unit (N112/9) (with code 351 (Emergency call system (HERMES)) or code 360 (HERMES UMTS) or code 362 (HERMES LTE))
• Over the user interface CAN, electronic ignition lock control unit and the diagnostics CAN to the emergency call system control unit (N123/4) (with code 348 (Emergency call/Assist system))

Depending on the type of transmission involved the following data, among others, are sent to the 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

Activation of 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.

Switching on interior lights 

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.

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.

Unlock central locking 

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 trunk lid or the liftgate enables access to aids such as the hazard warning triangle and first aid kit. Unlocking the fuel filler cap enables the QR code located on the fuel filler cap to be accessed. The QR code can be used by rescue services to quickly determine which rescue card applies for the vehicle in question.

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) (model 205.0/1/2, 253)
• Right rear door control unit (N69/4) (model 205.0/1/2, 253)

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

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.

Opening of 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.

Activation of crash-active easy exit feature (with code 275 (Memory package)) 

After an accident the crash-responsive exit aid is activated to make it easier for the driver to exit the vehicle or to enable first aiders to rescue the driver from the vehicle.

After a crash event has occurred, the driver seat and the steering column are automatically moved upwards to a defined position when the following actions are conducted.

• 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-2055-97FBA
	Overview of system components for supplemental restraint system		GF91.60-P-9996RF