Deploy supplemental restraint system, function

Function requirements, general

 Circuit 15R ON

 The electronic ignition lock control unit (N73) sends the status of circuit 15 via chassis CAN (CAN E) to the supplemental restraint system control unit (N2/10) and via interior CAN (CAN B) to the front SAM control unit with fuse and relay module (N10/1).

Deploying supplemental restraint system, general

The supplemental restraint system constantly monitors the occupation status of the front passenger seat and the status of the front seat belts (buckled or not buckled) and uses this information to adjust its deployment.

The supplemental restraint system deployment function comprises the following subfunctions:

 Function sequence system monitoring

 Function sequence for detecting occupied status of front passenger seat

 Function sequence for detecting status of front 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 end collision

 Function sequence for rollover (model 204.9 with code 494 (USA version))

 Function sequence for additional functions in the event of a crash

Function sequence system monitoring

The supplemental restraint system continuously monitors itself and signals faults to the driver via the supplemental restraint system indicator lamp (A1e15) in the instrument cluster (A1). The switch-on request for the supplement restraint system indicator lamp is sent by the supplement restraint system control unit via chassis CAN to the instrument cluster.

The automatic child seat recognition warning lamp (S6/1e1) (model 204.9, model 204.0/2 up to 28.02.2011 with code U18 (Automatic child seat recognition (ACSR [AKSE])) or code U10 (Automatic front passenger airbag shutoff)) in the instrument panel switch group (S6/1) is also switched on. The supplemental restraint system control unit sends the request to switch on the automatic child seat recognition warning lamp via chassis CAN to the front SAM control unit. The front SAM control unit actuates the automatic child seat recognition warning lamp via instrument panel LIN (LIN 1). Any faults are stored in the nonvolatile memory of the supplemental restraint system control unit. The supplemental restraint system indicator lamp and the automatic child seat recognition warning lamp are switched off following a successful self-test after t = 4 s.

 Model 204.3
as of model year 2015
with code 494 (US version)
Model 204.9
as of model year 2014
with code 494 (US version)
An event data recorder (event memory) is integrated into the supplemental restraint system control unit. Its task is to save data in certain accident situations from which an appraiser can get a better understanding of the behavior of the vehicle systems and the circumstances surrounding the accident. The stored data can be read out with the so-called crash data retrieval tool.

Function sequence for detecting occupied status of front passenger seat

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

The supplemental restraint system control unit receives the corresponding information from the following components:

 Front passenger seat occupancy recognition (B41/1) (except code U18 (Automatic child seat recognition (ACSR [AKSE])) and except code U10 (Automatic front passenger airbag shutoff)):

The status of the front passenger seat occupancy recognition is read in via a direct line in model 204.0/2/9 up to 28.02.2011 and model 204.3. In model 204.0/2/9 as of 01.03.2011, data is transferred via seat occupancy LIN (LIN E2).

 Front passenger seat occupancy recognition and ACSR [AKSE] (B48) (with code U18 (Automatic child seat recognition, ACSR [AKSE])):

The status of the front passenger seat occupancy recognition and ACSR is read in via a direct line in model 204.0/2/9 up to 28.02.2011 and model 204.3. In model 204.0/2/9 as of 01.03.2011, data is transferred via seat occupancy LIN.

 Weight sensing system (WSS) control unit (N110) (with code U10 (Automatic front passenger airbag shutoff)):

In model 204.0 up to 28.02.2011, model 204.9 up to 31.05.2011 and model 204.3, the weight applied to the front passenger seat is determined by means of a pressure measurement by the seat occupancy recognition pressure sensor (B48/4) in a seat mat filled with silicone. The force that is introduced via the seat belt is measured by the belt tension sensor (B48/3) so that weight classification corrections can be made if necessary. Based on these values, the WSS control unit classifies the applied weight and sends a corresponding signal via interior CAN, front SAM control unit and chassis CAN to the supplemental restraint system control unit.

In model 204.0 as of 01.03.2011 and model 204.9 as of 01.06.2011, the weight applied to the front passenger seat is determined by means of a pressure measurement by the WSS control unit. 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. Based on these two values, the WSS control unit classifies the applied weight and sends a corresponding signal via seat occupancy LIN to the supplemental restraint system control unit.

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

Function sequence for detecting status of front seat belts

The driver seat belt buckle restraint system switch (S68/3) or the front passenger seat belt buckle restraint system switch (S68/4) is actuated by the belt tab being inserted into the belt buckle. This is read in directly by the supplemental restraint system control unit.

 The status of the rear seat belts does not have any influence on the deployment behavior of the supplemental restraint system.

Function sequence for impact detection

The supplemental restraint system control unit determines the acceleration force acting upon the vehicle with the aid of the following sensors:

 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 204.0/2/9 with code 293 (Sidebags in rear))

 Right rear door pressure sensor (B48/10) (model 204.0/2/9 with code 293 (Sidebags in rear))

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

A distinction can be made between the following types of impact by evaluating these signals:

 Head-on collision

 Side-on collision

 Rear end collision

Function sequence for frontal impact

The supplemental restraint system control unit detects a frontal impact by evaluating the signals from the following components:

 Integrated sensors

 Left frontal acceleration sensor

 Right frontal acceleration sensor

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)

 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)

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

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:

The supplemental restraint system control unit uses the current occupancy to determine whether the front passenger airbag should be triggered at all or in 1 or 2 stages.

 Driver seat belt buckle status:

If the driver seat belt buckle restraint system switch detects that a belt tab is not inserted into the belt buckle, the driver airbag is triggered with advanced ignition timing instead of the driver emergency tensioning retractor.

 Front passenger seat belt buckle status:

If the front passenger seat belt buckle restraint system switch detects that a belt tab is not inserted into the belt buckle, the front passenger airbag is triggered with advanced ignition timing instead of the front passenger emergency tensioning retractor. However, this only applies if an occupied front passenger seat has been detected. Neither the emergency tensioning retractor nor the front passenger airbag is deployed if the seat is unoccupied.

Function sequence in the event of a side impact

The supplemental restraint system control unit detects a side impact by evaluating the signals from the following components:

 Integrated sensors

 Left sidebag sensor

 Right sidebag sensor

 Left front door pressure sensor

 Right front door pressure sensor

 Left rear door pressure sensor (model 204.0/2/9 with code 293 (Sidebags in rear))

 Right rear door pressure sensor (model 204.0/2/9 with code 293 (Sidebags in rear))

The restraint equipment is deployed depending on the severity of the impact and occupancy of the front passenger seat.

The following squibs can be ignited (at most):

 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 293 (Sidebags in rear))

 Right rear sidebag squib (R12/12) (with code 293 (Sidebags in rear))

 Left windowbag squib (R12/22)

 Right windowbag squib (R12/23)

 Driver pelvis airbag squib (R12/41) (with code 291 (PELVIS AIRBAG (PELVISBAG)))

 Front passenger pelvis airbag squib (R12/42) (with code 291 (PELVIS AIRBAG (PELVISBAG)))

The supplemental restraint system control unit makes a decision about triggering the front passenger sidebag unit based on the current occupation of the front passenger seat.

Function sequence for rear end collision

The supplemental restraint system control unit detects a rear-end collision by evaluating the signals from the following components:

 Integrated sensors

 Left sidebag sensor

 Right sidebag sensor

 Left frontal acceleration sensor

 Right frontal acceleration sensor

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 ETR [GUS] squib

 Front passenger ETR [GUS] squib

 Left rear emergency tensioning retractor squib

 Right rear emergency tensioning retractor squib

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

The following components are also actuated by the supplemental restraint system control unit:

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

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

The following situations are taken into account:

 Driver seat belt buckle status:

If the driver belt buckle restraint system switch detects that a belt tab has not been inserted into the belt buckle, the driver emergency tensioning retractor is not deployed.

 Front passenger seat belt buckle status:

If the front passenger belt buckle restraint system switch detects that a belt tab has not been inserted into the belt buckle, the front passenger emergency tensioning retractor is not deployed.

Function sequence for rollover (model 204.9 with code 494 (USA version))

The supplemental restraint system control unit detects a rollover by evaluating the signals from the integrated sensors.

The following squibs can be ignited (at most):

 Driver ETR [GUS] squib

 Front passenger ETR [GUS] squib

 Left rear emergency tensioning retractor squib

 Right rear emergency tensioning retractor squib

The following situations are taken into account:

 Driver seat belt buckle status:

If the driver belt buckle restraint system switch detects that a belt tab has not been inserted into the belt buckle, the driver emergency tensioning retractor is not deployed.

 Front passenger seat belt buckle status:

If the front passenger belt buckle restraint system switch detects that a belt tab has not been inserted into the belt buckle, the front passenger emergency tensioning retractor is 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 opening the central locking (CL [ZV])

 Function sequence for opening the side windows

 Function sequence for shutting off the engine

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

 Function sequence for switching off stationary heater (STH) (with CODE 228 (Stationary heater))

 Function sequence for automatic emergency call (with CODE 359 (TELEAID emergency call system) or CODE 348 (Emergency call/assist system))

 Function sequence for activating the crash-active easy exit function (with CODE 275 (Memory package))

Function sequence for activating the hazard warning function

The hazard warning flasher function is activated automatically in order to warn other road users in the event of an accident. The crash signal is sent by the supplemental restraint system control unit over the chassis CAN to the front SAM control unit. The front SAM control unit initiates the hazard warning flasher function by issuing the flasher frequency via 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 when it is dark, the interior illumination is automatically activated. The crash signal is sent by the supplemental restraint system control unit over the chassis CAN to the front SAM control unit. The front SAM control unit then activates the interior illumination.

Function sequence for opening the central locking (CL [ZV])

In order to make it possible for persons giving assistance to gain access to vehicle occupants who may be injured in the event of an accident, the central locking (CL [ZV]) is automatically unlocked.

The supplemental restraint system control unit transmits the crash signal via the chassis CAN, the front SAM control unit and the interior CAN to the following control units

 Left front door control unit (N69/1)

 Right front door control unit (N69/2)

 Left rear door control unit (N69/3) (model 204.0/2/9)

 Right rear door control unit (N69/4) (model 204.0/2/9)

The central locking (CL [ZV]) is then unlocked after a waiting time of t = 8 to 11 s. In the event of rear end collision, the CL is unlocked without waiting time.

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 are opened automatically in order to allow these smoke particles to quickly disperse.

The supplemental restraint system control unit transmits the crash signal via the chassis CAN, the front SAM control unit and the interior CAN to the following control units

 Left front door control unit

 Right front door control unit

 Left rear door control unit (in model 204.0/2/9)

 Right rear door control unit (in model 204.0/2/9)

Function sequence for shutting off the engine

After an accident, the engine is automatically turned off to reduce the risk of fire. The supplemental restraint system control unit sends the crash signal via the chassis CAN 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.

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

In order to prevent hazardous gases from entering the vehicle interior after an accident, the automatic air conditioning control and operating unit (N22/7) shuts off the air conditioning and closes the air recirculation flap. The supplemental restraint system control unit transmits the crash signal via the chassis CAN, the front SAM control unit and the interior CAN to the automatic climate control control and operating unit.

Function sequence for shutting off stationary heater (with CODE 228 (Stationary heater))

After an accident, the stationary heater is automatically turned off to reduce the risk of fire. The supplemental restraint system control unit sends the crash signal via the chassis CAN, front SAM control unit and interior CAN to the stationary heater control unit (A6n1), which prompts a shutoff of the stationary heater.

Function sequence for automatic emergency call (with CODE 359 (TELEAID emergency call system) or CODE 348 (Emergency call/assist system))

An emergency call is made automatically after an accident. The supplemental restraint system control unit transmits the crash signal via the chassis CAN, the front SAM control unit and the diagnostic CAN (CAN D) to the emergency call system control unit (N123/4), which makes the automatic emergency call.

 The crash signal is also sent over a direct line from the supplemental restraint system control unit to the emergency call system control unit.

Function sequence for activating the crash-active easy exit function (with CODE 275 (Memory package))

In order to make it easier for the driver to get out of the vehicle and for first aiders to recover the driver from the vehicle after an accident, the steering column is automatically moved upwards in the event of 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, 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.