Deploy supplemental restraint system, function - GF91.60-P-2001CE

MODEL 204.0/2 as of model year 2009 

MODEL 204.3 

MODEL 204.9 

Function requirements, general 

• Circuit 15R ON

The status of circuit 15 is transmitted by the electronic ignition lock control unit (N73) via the chassis CAN (CAN E) to the supplemental restraint system control unit (N2/10) and via the 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 evaluation of occupancy 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 for side impact 
• Function sequence for rear end collision 
• Function sequence for rollover (in 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) (in model 204.9, model 204.0/2 up to 28.2.11 with code (U18) Automatic child seat recognition (ACSR) or code (U10) Front passenger seat with weight detection) in the instrument panel switch group (S6/1) or the automatic child seat recognition airbag off indicator lamp (N72/1e1) (in model 204.0/2 as of 1.3.11, model 204.3 with code (U18) Automatic child seat recognition (ACSR) or code (U10) Front passenger seat with weight detection) in the upper control panel control unit (N72/1) is also switched on. The request to switch on the relevant automatic child seat recognition warning or indicator lamp is transmitted by the supplemental restraint system control unit via the chassis CAN to the front SAM control unit. The front SAM control unit actuates the automatic child seat recognition warning or indicator lamp via the 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 or indicator lamp are switched off after t = 4 s after a successful self-test.

In model 204.9 with code (494) USA version an accident data recorder is integrated in the supplemental restraint system control unit. This works in principle like the "black box" known from aviation. The course of the accident can be reconstructed using the stored data.

Function sequence for evaluation of occupancy status of front passenger seat 

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

Without code (U18) Automatic child seat recognition (ACSR) and without code (U10) Front passenger seat with weight sensing, the status of the seat occupied recognition does not have any influence on the deployment behavior of the supplemental restraint system.

Detailed information about the seat occupied recognition can be found in the subfunction "Passenger-side seat occupied recognition, function".

Function sequence for detecting status of front seat belts 

The deployment behavior of the front restraint equipment is adapted on the basis of the seat belt status (worn or not being worn). 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 latch 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) Rear left and right sidebags)
• Right rear door pressure sensor (B48/10) (model 204.0/2/9 with code (293) Rear left and right sidebags)

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

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

• Head-on collision
• Side-on collision
• Rear end collision
• Rollover (model 204.9 with code (494) USA version)

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)
• 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 decide about suppression or 1 or 2-stage deployment of the front passenger airbag unit.

• Driver belt buckle status:

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

• Front passenger belt buckle status:

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

  This only applies, however, if the front passenger seat is known to be occupied. If the seat is unoccupied, neither the emergency tensioning retractor nor the front passenger airbag unit are deployed.

Function sequence for 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) Left and right rear sidebags)
• Right rear door pressure sensor (model 204.0/2/9 with code (293) Left and right rear sidebags)

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) Left and right rear sidebag)
• Right rear sidebag squib (R12/12) (with code (293) Left and right rear sidebag)
• 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 squibs are actuated directly by the supplemental restraint system control unit.

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) (except model 204.077/277/377)
• Front passenger seat NECK-PRO head restraint solenoid (Y24/13) (except model 204.077/277/377)

The following situations are taken into account:

• Driver belt buckle status:

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

• Front passenger belt buckle status:

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

Function sequence for rollover (in 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. Only one roll-over around the longitudinal vehicle axis can be detected.

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 situations are taken into account:

• Driver belt buckle status:

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

• Front passenger belt buckle status:

  If the front passenger belt buckle restraint system switch detects that a belt latch has not been inserted into the belt buckle, the front passenger emergency tensioning retractor unit 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 flasher function 
• Function sequence for switching on the 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 1.6.13) 
• Function sequence for shutting off the stationary heater (STH) (with code (228) Stationary heater) 
• Function sequence for automatic emergency call (in model 204.0/3/9 with code (359) TELEAID emergency call system or code (348) Emergency call/Assist system) 
• Function sequence for activating crash-active easy exit (with code (275) Memory package (Driver seat, steering column, mirrors)) 

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 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.

Detailed information about the hazard warning flasher function can be found in the separate function description "Exterior lights, function" in subfunction "Turn signal light actuation, function".

Function sequence for switching on the interior illumination 

In order to make it easier for the vehicle occupants or persons giving assistance to find their way around inside the vehicle in the event of an accident, 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.

Detailed information on interior illumination can be found in the separate function description "Interior illumination (IBL), function" in the subfunction "Automatic interior lights control, function".

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

In order to make it possible for helpers gain access to vehicle occupants who may be injured in the event of an accident, the CL [ZV] is unlocked automatically. 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 implements the "Emergency opening" request.

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

Detailed information about the CL [ZV] can be found in the "Central locking (CL [ZV]), function" subfunction of the separate function description "Theft protection and locking function description".

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 leaving a gap 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 (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)

Detailed information on opening the side windows can be found in the separate function description "Power windows (EFH), function".

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 transmits the crash signal via the chassis CAN to the CDI control unit (N3/9) (with diesel engine) or to the ME-SFI [ME] control unit (N3/10) (with gasoline engine). This then causes the engine to be shut off.

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

Function sequence for switching off the air conditioning system (as of 1.6.13) 

In order to prevent hazardous gases from entering the vehicle interior after an accident, the automatic climate control control and operating unit (N22/7) shuts off the air conditioning and closes the fresh air/recirculated air 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.

Detailed information about switching off the air conditioning can be found in the separate function description "Automatic climate control, function" in the "Automatic climate control regulation, function" subfunction.

Function sequence for shutting off the stationary heater (STH) (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 transmits the crash signal via the chassis CAN, the front SAM control unit and the interior CAN to the stationary heater control unit (A6n1), which prompts a shutoff of the stationary heater.

Detailed information about the stationary heater can be found in the separate function description "Stationary heater (STH), function".

Function sequence for automatic emergency call (in model 204.0/3/9 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 transmitted via a direct line from the supplemental restraint system control unit to the emergency call system control unit.

Detailed information about the automatic emergency call can be found in the separate "Telematics" function description in the "Emergency call system function" subfunction.

Function sequence for activating crash-active easy exit (with code (275) Memory package (Driver seat, steering column, mirrors)) 

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.

Detailed information about the crash-active easy exit feature can be found in the separate "Electrical seats, function" function description in the "Electrically adjustable steering column (ESC [EVL]), function" subfunction.

	Electrical function schematic, supplemental restraint system (SRS)		PE91.60-P-2052-97FAB
	Overview of supplemental restraint system (SRS) system components		GF91.60-P-9998CE