Actuate supplemental restraint system, function

Function requirements, general

 Circuit 15R ON

 The electronic ignition lock control unit (N73) transmits the circuit 15 status via the chassis CAN (CAN E) (up to 29.02.2016) or via chassis CAN 1 (CAN E1) (as of 01.03.2016) to the Supplemental Restraint System control unit (N2/10).

Actuate Supplemental Restraint System, general

The supplemental restraint system continuously 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 front passenger seat occupancy status evaluation

 Function sequence for recognition of seat belt status

 Function sequence for impact detection

 Function sequence for frontal impact deployment

 Function sequence for side impact deployment

 Function sequence for rear end collision deployment

 Function sequence for rollover deployment

 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 (A1e15) in the instrument cluster (A1)

 Automatic child seat recognition airbag OFF indicator lamp(N72/1e1) and automatic child seat recognition airbag ON indicator lamp (N72/1e4) in the upper control panel control unit (N72/1)

Following a successful self-test (t = 4 s) the supplemental restraint system indicator lamp is then switched off. The respective occupancy status of the front passenger seat is shown via the automatic child seat recognition airbag OFF indicator lamp or the automatic child seat recognition airbag ON indicator lamp.

The Supplemental Restraint System control unit transmits the request to switch on the Supplemental Restraint System indicator lamp in vehicles up to 29.02.2016 via the chassis CAN and in vehicles as of 01.03.2016 via chassis CAN 1, the front SAM control unit with fuse and relay module (N10/1) and chassis CAN 2 (CAN E2) to the instrument cluster. The Supplemental Restraint System control unit transmits the request to switch on the respective automatic child seat recognition indicator lamp via the chassis CAN (up to 29.02.2016) or chassis CAN 1 (as of 01.03.2016), the front SAM control unit and the instrument panel LIN (LIN 1) to the upper control panel control unit, which directly actuates the respective automatic child seat recognition indicator lamp.

The supplemental restraint system control unit constantly monitors the supplemental restraint system when driving and reports faults to the driver via the multifunction display (A1p13) and the supplemental restraint system indicator lamp in the instrument cluster. The Supplemental Restraint System control unit transmits the request to display an appropriate message in vehicles up to 29.02.2016 via the chassis CAN and in vehicles as of 01.03.2016 via chassis CAN 1, the front SAM control unit and chassis CAN 2 to the instrument cluster. The faults are stored in the nonvolatile memory of the supplemental restraint system control unit.

 Model 172.4 as of 12/1/13
with code 494 (US version)
An accident data recorder is integrated in the supplemental restraint system control unit, which records relevant data before, during and after an accident. The data stored can be used to trace back the course of the accident.

Function sequence for front passenger seat occupancy status evaluation

The supplemental restraint system control unit adapts the deployment behavior of the restraint equipment at the front passenger side to the occupancy status of the front passenger seat.

Function sequence for recognition of seat belt status

The Supplemental Restraint System control unit adjusts the triggering behavior of the restraint equipment to the status of the seat belts (fastened or not fastened). The status of the respective seat belt is defined via the corresponding switch:

 Driver belt buckle restraint system switch (S68/3)

 Front passenger belt buckle restraint system switch (S68/4)

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

Function sequence for impact detection

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

 Head-on collision

 Side-on collision

 Rear end collision

 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 door pressure sensor (B48/7)

 Right door pressure sensor (B48/8)

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

Function sequence for frontal impact deployment

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

The following squibs can be ignited (at most):

 Driver emergency tensioning retractor squib (R12/1) (model 172.466/475 with code 494 (USA version) or code 460 (Canada version))

 Front passenger emergency tensioning retractor squib (R12/2) (model 172.466/475 with code 494 (USA version) or code 460 (Canada version))

 Front passenger airbag squib 1 (R12/4)

 Front passenger airbag squib 2 (R12/5)

 Driver airbag squib 1 (R12/13)

 Driver airbag squib 2 (R12/14)

 Front passenger kneebag squib (R12/24) (with CODE 294 (Kneebag))

 Driver kneebag squib (R12/25) (with CODE 294 (Kneebag))

 Drive buckle ETR squib (R46)

 Front passenger emergency tensioning retractor squib (R46/1)

The supplemental restraint system control unit directly actuates the squibs.

The following situations are taken into account:

 Occupancy status of the front passenger seat:

The supplemental restraint system control unit uses the current occupancy to decide about suppression or 1 or 2-stage deployment of the front passenger airbag.

 Driver seat belt buckle status:

If the seat belt is not fastened, the driver airbag is deployed with advanced ignition timing instead of the emergency tensioning retractor (model 172.466/475 with code 494 (USA version) or code 460 (Canada version)) and the buckle emergency tensioning retractor.

 Front passenger seat belt buckle status:

If the seat belt is not fastened, the front passenger airbag is deployed with advanced ignition timing instead of the emergency tensioning retractor (model 172.466/475 with code 494 (USA version) or code 460 (Canada version)) and the buckle emergency tensioning retractor. However, this only applies if an occupied front passenger seat has been detected. No restraint equipment is triggered at the passenger side if the seat is unoccupied or the seat belt is not fastened.

Function sequence for side impact deployment

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

The following squibs can be ignited (at most):

 Driver emergency tensioning retractor squib (model 172.466/475 with code 494 (USA version) or code 460 (Canada version))

 Front passenger emergency tensioning retractor squib (model 172.466/475 with code 494 (USA version) or code 460 (Canada version))

 Driver sidebag squib (R12/9)

 Front passenger sidebag squib (R12/10)

 Left headbag squib (R12/39)

 Right headbag squib (R12/40)

 Driver buckle ETR squib

 Front passenger buckle ETR squib

The supplemental restraint system control unit directly actuates the squibs.

The following situations are taken into account:

 Occupancy status of the front passenger seat:

The supplemental restraint system control unit uses the current occupancy status of the front passenger seat to decide whether the passenger side sidebag and headbag are triggered.

 Driver seat belt buckle status:

If the seat belt is not fastened, the emergency tensioning retractor (model 172.466/475 with code 494 (USA version) or code 460 (Canada version)) and the buckle emergency tensioning retractor at the driver side are not deployed.

 Front passenger seat belt buckle status:

If the seat belt is not fastened, the emergency tensioning retractor (model 172.466/475 with code 494 (USA version) or code 460 (Canada version)) and the buckle emergency tensioning retractor at the passenger side are not deployed.

Function sequence for 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 (at most):

 Driver emergency tensioning retractor squib (model 172.466/475 with code 494 (USA version) or code 460 (Canada version))

 Front passenger emergency tensioning retractor squib (model 172.466/475 with code 494 (USA version) or code 460 (Canada version))

 Driver buckle ETR squib

 Front passenger buckle ETR squib

The following components can be actuated additionally:

 Driver seat NECK-PRO head restraint solenoid (Y24/12)

 Front passenger seat NECK-PRO head restraint solenoid (Y24/13)

The supplemental restraint system control unit directly actuates the squibs and the NECK-PRO head restraint solenoids.

The following situations are taken into account:

 Driver seat belt buckle status:

If the seat belt is not fastened, the emergency tensioning retractor (model 172.466/475 with code 494 (USA version) or code 460 (Canada version)) and the buckle emergency tensioning retractor at the driver side are not deployed.

 Front passenger seat belt buckle status:

If the seat belt is not fastened, the emergency tensioning retractor (model 172.466/475 with code 494 (USA version) or code 460 (Canada version)) and the buckle emergency tensioning retractor at the passenger side are not deployed.

Function sequence for rollover deployment

The restraint equipment is deployed depending on the occupancy of the front passenger seat and the status of the seat belts.

The following squibs can be ignited (at most):

 Driver emergency tensioning retractor squib (model 172.466/475 with code 494 (USA version) or code 460 (Canada version))

 Front passenger emergency tensioning retractor squib (model 172.466/475 with code 494 (USA version) or code 460 (Canada version))

 Driver sidebag squib

 Front passenger sidebag squib

 Left headbag squib

 Right headbag squib

 Driver buckle ETR squib

 Front passenger buckle ETR squib

The supplemental restraint system control unit directly actuates the squibs.

The following situations are taken into account:

 Occupancy status of the front passenger seat:

The supplemental restraint system control unit uses the current occupancy status of the front passenger seat to decide whether the passenger side sidebag and headbag are triggered.

 Driver seat belt buckle status:

If the seat belt is not fastened, the emergency tensioning retractor (model 172.466/475 with code 494 (USA version) or code 460 (Canada version)) and the buckle emergency tensioning retractor at the driver side are not deployed.

 Front passenger seat belt buckle status:

If the seat belt is not fastened, the emergency tensioning retractor (model 172.466/475 with code 494 (USA version) or code 460 (Canada version)) and the buckle emergency tensioning retractor at the passenger side are not deployed.

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 function

 Function sequence for switching on interior illumination

 Function sequence for unlocking the central locking

 Function sequence for lowering side windows

 Function sequence for shutting off the engine

 Function sequence for triggering the pyrofuse

 Function sequence for switching off the air conditioning system (as of 01.06.2013)

 Function sequence for automatic emergency call (up to 29.02.2016 with code 347 (Mercedes-Benz emergency call system), code 348 (Emergency call/assist system) or code 359 (TELEAID emergency call system), as of 01.03.2016 with code 350 (eCall Europe emergency call system) or code 494 (USA version))

 Function sequence for activating the crash-active steering column adjustment (with CODE 275 (Memory package))

Function sequence for activating the hazard warning function

In the event of an accident, the hazard warning flasher function is activated automatically in order to warn other road users. The Supplemental Restraint System control unit transmits the crash signal via the chassis CAN (up to 29.02.2016) or chassis CAN 1 (as of 01.03.2016) to the front SAM control unit. The front SAM control unit then activates the hazard warning flasher function.

Function sequence for switching on interior illumination

After an accident the interior illumination is switched on to make orientation easier for the vehicle occupants or persons giving assistance. The Supplemental Restraint System control unit transmits the crash signal via the chassis CAN (up to 29.02.2016) or chassis CAN 1 (as of 01.03.2016) to the front SAM control unit. The front SAM control unit then activates the interior illumination.

Function sequence for unlocking the central locking

After an accident, the doors, the trunk lid and the tank cap are automatically unlocked via the central locking system. The unlocking of the doors allows rescuers to gain access to any vehicle occupants who may be injured. The unlocking of the trunk lid enables access to aids such as the hazard warning triangle and first aid kit. 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 corresponding rescue card for the vehicle.

The Supplemental Restraint System control unit transmits the crash signal via the chassis CAN (up to 29.02.2016) or chassis CAN 1 (as of 01.03.2016), the front SAM control unit and the interior CAN (CAN B) to the following control units:

 Rear SAM control unit with fuse and relay module (N10/2)

 Left door control unit (N69/1)

 Right door control unit (N69/2)

The central locking is unlocked after a waiting time of t = 8 to 11 s.

Additional function requirements for lowering the side windows

 Power windows normalized

 Side windows closed further than "Crash Position"

Function sequence for lowering side windows

After an accident, the front side windows are opened to a defined position. This allows the smoke particles generated by the pyrotechnical restraint equipment to disperse quickly when the Vario roof is closed. The Supplemental Restraint System control unit transmits the crash signal via the chassis CAN (up to 29.02.2016) or chassis CAN 1 (as of 01.03.2016), the front SAM control unit and the interior CAN to the left door control unit and the right door control unit. These then cause the side windows to be lowered.

Function sequence for shutting off the engine

After an accident, the engine is automatically switched off and the fuel supply stopped to reduce the fire hazard risk. The Supplemental Restraint System control unit transmits the crash signal via chassis CAN (up to 29.02.2016) or chassis CAN 1 (as of 01.03.2016) to the CDI control unit (N3/9) (diesel engine) or 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 triggering the pyrofuse

After an accident, pyrofuse 88 (F32/5f88) (except code B03 (ECO start/stop function)) or pyrofuse (F63) (with code B03 (ECO start/stop function)) is triggered to reduce the risk of fire.

 By triggering the respective pyrofuse, the starter (M1) and the alternator (G2) are disconnected from the on-board electrical system.

P91.60-3611-71

The main line inside the respective pyrofuse housing is designed as busbar with a predetermined fracture point (3). After a crash event occurs, the Supplemental Restraint System control unit directly actuates the respective pyrofuse. 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:

Piston movement starts after t = 300 μs.

Bus bar disconnection is complete after t = 450 μs.

Function sequence for switching off the air conditioning system (as of 01.06.2013)

After an accident, the air conditioning is switched off and the air recirculation flap is closed in order to prevent harmful gases entering the vehicle interior. The Supplemental Restraint System control unit transmits the crash signal via the chassis CAN (up to 29.02.2016) or chassis CAN 1 (as of 01.03.2016), the front SAM control unit and the interior CAN to the automatic air conditioning control and operating unit (N22/7).

Function sequence for automatic emergency call (up to 29.02.2016 with code 347 (Mercedes-Benz emergency call system), code 348 (Emergency call/assist system) or code 359 (TELEAID emergency call system), as of 01.03.2016 with code 350 (eCall Europe emergency call system) or code 494 (USA version))

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

 Direction of travel

 Vehicle identification number

 Mercedes-Benz Contact coding

 Indicator for automatic or manual triggering

 Time stamp

Function sequence for activating the crash-active steering column adjustment (with CODE 275 (Memory package))

After an accident, the steering column is moved upwards in order to allow the driver to exit the vehicle or to allow first aiders to help the driver out of the vehicle. The function is triggered with the following actions:

 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 chassis CAN (up to 29.02.2016) or chassis CAN 1 (as of 01.03.2016), the front SAM control unit and the interior CAN to the driver seat control unit (N32/1), which controls the crash-active easy exit function.