Deploy supplemental restraint system, function - GF91.60-P-2001LE
MODEL 216.3, 221.0 /1 as of model year 2009
/YoM 08
Function requirements, general
- Circuit 5R On
Triggering supplemental restraint system (SRS), general
The SRS is continuously monitoring the occupation status of the front passenger seat, the status of the front seat belts (buckled or not buckled) and adjusts its deployment behavior with the help of this information.
The trigger SRS function consists of the following subfunctions:
- Function sequence system monitoring
- Function sequence for evaluation of front passenger seat occupation condition
- Function sequence for evaluation of front seat belts status
- Function sequence for evaluation of speed relative to opposing object (model 221 as of 1.6.09 with code (233) DISTRONIC PLUS)
- 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
- Function sequence for belt lock system (model 221)
- Function sequence power reserve
- Function sequence of 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 airbag indicator and warning lamp (A1e15) in the instrument cluster (A1). In addition, the automatic child seat recognition airbag OFF indicator lamp (S6/2e1) in the cockpit switch group (S6/2) is switched on. All faults are stored in the nonvolatile memory of the restraint systems control unit (N2/7). The airbag indicator and warning lamp and the automatic child seat recognition airbag OFF indicator lamp are switched off after t = 4 s following a successful self-test.
Function sequence for evaluation of front passenger seat occupation condition
The restraint systems control unit receives the corresponding information from the following components:
- Front passenger seat occupied recognition (B41/1)
(without code (U18) Automatic child seat recognition (ACSR [AKSE]) and without code (494) USA version)
- Front passenger seat occupied recognition and automatic child seat recognition (B48)
(with code (U18) Automatic child seat recognition (ACSR [AKSE]))
- WSS control unit (weight sensing system) (N2/13)
(Model 221 with code (494) USA version up to 31.8.08)
- Weight sensing system control unit (WSS) (N110)
(Model 216 with code (494) USA version, model 221 with code (494) USA version as of 1.9.08)
Without code (U18) Automatic child seat recognition (ACSR [AKSE]) and without code (494) USA version, the status of the front passenger seat occupied recognition has no influence on the deployment behavior of the SRS. This information is only used to produce the seat belt reminder warning. In this case, the deployment behavior of the supplemental restraint system is dependent on the seat fore/aft position of the front passenger seat. The seat fore/aft position is sent by the right front seat control unit (N32/2) (on left-hand drive vehicle) or by the left front seat control unit (N32/1) (on right-hand drive vehicle) via interior CAN (CAN B) to the central gateway control unit (N93). The signal is read in by the restraint systems control unit via chassis CAN (CAN E).
Function sequence for evaluation of front seat belts status
The driver seat belt buckle and seat belt reminder warning switch (S68/1) or the front passenger seat belt buckle and seat belt reminder warning switch (S68/2) is actuated by the belt latch which is inserted into the seat belt buckle. This is read in directly by the restraint systems control unit.
The status of the rear seat belts does not have any influence on the deployment behavior of the SRS.
Function sequence for evaluation of speed relative to opposing object (model 221 as of 1.6.09 with code (233) DISTRONIC PLUS)
The speed relative to the opposing object is evaluated for deployment of the SRS. The radar sensors control unit (SGR) (N62/1) (up to 31.8.10) or the video and radar sensor system control unit (N62/2) (as of 1.9.10) constantly records the surroundings of the front of the vehicle using radar.
The radar sensors control unit or the video and radar sensor system control unit sends the recorded relative speed and the time until impact via vehicle dynamics CAN (CAN H) to the ESP control unit (N47-5).
The ESP control unit sends the data via chassis CAN to the restraint systems control unit. The restraint systems control unit evaluates the data and calculates the severity of the impact to be expected. The data of the sensors specified in the function sequence for impact detection are still evaluated for the actual deployment of the SRS.
The radar sensors control unit or the video and radar sensor system control unit also records the vehicle surroundings with deactivated DISTRONIC PLUS and when the vehicle is at a standstill.
Function sequence for impact detection
The restraint systems control unit determines the acceleration acting on the vehicle with the aid of its integrated sensor and the following sensors:
- Driver-side frontal acceleration sensor (B48/1)
- Passenger-side frontal acceleration sensor (B48/2)
- Airbag system driver assist (B48/5)
- Airbag system front passenger assist (B48/6)
- Driver door pressure sensor (B48/7)
- Front passenger door pressure sensor (B48/8)
- Rear door pressure sensor, driver-side (B48/9) (model 221)
- Rear door pressure sensor, passenger-side (B48/10) (model 221)
With the aid of this sensor system, the SRS is able to distinguish between the following types of impacts:
- Head-on collision
- Side-on collision
- Rear end collision
- Roll-over
Function sequence for frontal impact
A frontal impact is detected by the restraint systems control unit via the signals from the following components:
- Integrated sensor in the restraint systems control unit
- Driver-side frontal acceleration sensor
- Passenger-side frontal acceleration sensor
The restraint equipment is deployed depending on the severity of the impact, the occupation of the front passenger seat and the status of the front seat belts.
The following squibs can be ignited (at most):
- Passenger airbag squib 1 (R12/4)
- Passenger airbag squib 2 (R12/5)
- Left rear ETR squib (R12/6)
- Right rear ETR squib (R12/7)
- Driver airbag squib 1 (R12/13)
- Driver airbag squib 2 (R12/14)
- Driver kneebag squib (R12/25) (with code (294) Kneebag)
- Drive buckle ETR squib (R46)
- Front passenger ETR squib (R46/1)
The following situations are taken into account:
- Speed relative to the opposing object
- Occupied state of the front passenger seat:
The restraint systems control unit uses the current occupancy to decide whether to suppress the front passenger airbag unit or to use 1-stage or 2-stage deployment.
- Driver seat belt buckle status:
If the driver seat belt buckle and seat belt reminder warning switch detects that a belt latch is not inserted into the seat belt buckle, the driver airbag unit with advanced ignition timing is triggered instead of the driver buckle emergency tensioning retractor unit.
- Front passenger seat belt buckle status:
If the front passenger seat belt buckle and set belt reminder warning switch detects that a belt latch is not inserted into the seat belt buckle, the front passenger airbag unit with advanced ignition timing is triggered instead of the front passenger buckle emergency tensioning retractor unit.
The status of the seat belt buckles is only evaluated with an occupied front passenger seat. If the seat is not occupied, neither the buckle emergency tensioning retractor nor the front passenger airbag unit are deployed.
Function sequence for side impact
A side impact is detected by the restraint systems control unit via the signals from the following components:
- Integrated sensor in the restraint systems control unit
- Airbag system driver assist
- Airbag system front passenger assist
- Driver door pressure sensor
- Front passenger door pressure sensor
- Rear door pressure sensor, driver side (model 221)
- Rear door pressure sensor, passenger side (model 221)
The restraint equipment is deployed depending on the severity of the impact and the occupation of the front passenger seat.
The following squibs can be ignited (at most):
- Left rear sidebag squib (R12/11)
- Right rear sidebag squib (R12/12)
- Front left sidebag squib (R12/20)
- Front right side air bag squib (R12/21)
- Left rear windowbag squib (R12/22)
- Right rear windowbag squib (R12/23)
The following state is taken into consideration:
- The restraint systems control unit makes its decision regarding triggering the front passenger sidebag unit based on the current occupancy of the front passenger seat.
Function sequence for rear end collision
A rear end collision is detected by the restraint systems control unit via the signals from the following components:
- Integrated sensor in the restraint systems control unit
- Driver-side frontal acceleration sensor
- Passenger-side frontal acceleration sensor
- Airbag system driver assist
- Airbag system front passenger assist
The restraint equipment is deployed depending on the severity of the impact and the status of the front seat belts.
The following squibs can be ignited (at most):
- Driver buckle ETR squib
- Front passenger buckle ETR squib
- Left rear ETR squib
- Right rear ETR squib
The following components are actuated (model 221):
- Driver NECK-PRO head restraint solenoid (Y24/12)
- Front passenger NECK-PRO head restraint solenoid (Y24/13)
The following situations are taken into account:
- Driver seat belt buckle status:
If the driver seat belt buckle and seat belt reminder warning switch detects that a belt latch is not inserted into the seat belt buckle, the driver emergency tensioning retractor unit is not triggered.
- Front passenger seat belt buckle status:
If the front passenger seat belt buckle and seat belt reminder warning switch detects that a belt latch is not inserted into the seat belt buckle, the front passenger buckle emergency tensioning retractor unit is not triggered.
Function sequence for rollover
A roll over is detected by the restraint systems control unit using the signals from the following components:
- Integrated sensor in the restraint systems control unit
- Driver-side frontal acceleration sensor
- Passenger-side frontal acceleration sensor
- Airbag system driver assist
- Airbag system front passenger assist
The following squibs can be ignited (at most):
- Driver buckle ETR squib
- Front passenger buckle ETR squib
- Left rear ETR squib
- Right rear ETR squib
The following situations are taken into account:
- Driver seat belt buckle status:
If the driver seat belt buckle and seat belt reminder warning switch detects that a belt latch is not inserted into the seat belt buckle, the driver emergency tensioning retractor unit is not triggered.
- Front passenger seat belt buckle status:
If the front passenger seat belt buckle and seat belt reminder warning switch detects that a belt latch is not inserted into the seat belt buckle, the front passenger emergency tensioning retractor unit is not triggered.
Function sequence for belt lock system (on model 221)
Irrespective of the restraint systems control unit, the belt is mechanically prevented from extending in certain situations.
Function sequence power reserve
The restraint systems control unit provides power reserves for at least t = 300 ms if the battery has been disconnected.
Function sequence of additional functions in the event of a crash
The additional functions in the event of a crash comprise the following subfunctions:
- Function sequence for activation of hazard warning function
- Function sequence for activation of the interior illumination
- Function sequence for opening the central locking (CL [ZV])
- Function sequence for opening the side windows
- Function sequence for opening the tilting/sliding roof (on model 221 with code (414) Power glass tilting/sliding roof, on model 216)
- Function sequence for shutting off the engine
- Function sequence for shutting off the stationary heater (STH) (with code (228) Stationary heater)
- Function sequence for automatic emergency call (with code (359) TELE AID emergency call system)
Function sequence for activation of hazard warning function
The hazard warning function is activated automatically after a crash event has occurred. The crash signal is transmitted by the restraint systems control unit via the chassis CAN to the central gateway control unit. This routes the signal on the interior CAN to the rear SAM control unit with fuse and relay module (N10/2), which functions as a flash master.
The rear SAM control unit sends the hazard warning flashing request via interior CAN to the following control units:
- Front SAM control unit with fuse and relay module (N10/1)
- Left door control unit (N69/1) (model 216) or Left front door control unit (N69/1) (model 221)
- Right door control unit (N69/2) (model 216) or Right front door control unit (N69/2) (model 221)
Detailed information is available in the separate function description "Exterior lights".
Function sequence for activation of the interior illumination
The interior illumination is activated automatically after a crash event has occurred. The crash signal is transmitted by the restraint systems control unit via the chassis CAN to the central gateway control unit. This routes the signal on the interior CAN to the overhead control panel control unit (N70), which activates the interior illumination.
Detailed information is available in the separate function description "Interior illumination".
Function sequence for opening the central locking (CL [ZV])
The CL [ZV] is unlocked automatically after a crash event has occurred (waiting time of t = 8 s to t = 11 s). The crash signal is transmitted by the restraint systems control unit via the chassis CAN to the central gateway control unit. This sends the open CL [ZV] request on the interior CAN to the following control units:
- Left door control unit or front left door control unit
- Right door control unit or front right door control unit
- Left rear door control unit (N69/3) (model 221)
- Right rear door control unit (N69/4) (model 221)
Detailed information is available in the separate function description "Central locking".
Function sequence for opening the side windows
After a crash event has occurred, the side windows are automatically opened by approx. s = 50 mm. The purpose of opening the side windows is to speed up the extraction of the smoke particles generated by the pyrotechnical restraint equipment. The crash signal is transmitted by the restraint systems control unit via the chassis CAN to the central gateway control unit. This routes the signal on the interior CAN to the following control units:
- Left door control unit or front left door control unit
- Right door control unit or front right door control unit
- Left rear door control unit (model 221)
- Right rear door control unit (model 221)
- Rear control unit (N22/6) (model 216)
Detailed information is available in the separate function description "Power window".
Function sequence for opening the tilting/sliding roof (on model 221 with code (414) Power glass tilting/sliding roof, on model 216)
After a crash event has occurred, the tilting/sliding roof or panoramic sliding sunroof is automatically opened by approx. s = 50 mm. By opening the tilting/sliding roof, the extraction of the smoke particles generated by the pyrotechnical restraint equipment is to be sped up.
The crash signal is transmitted by the restraint systems control unit via the chassis CAN to the central gateway control unit. This routes the signal on the interior CAN to the overhead control panel control unit.
Detailed information is available in the separate function description "Tilting/sliding roof (SHD)".
Function sequence for shutting off the engine
The engine is shut off automatically after a crash event has occurred. The crash signal is sent by the restraint systems control unit via chassis CAN to the CDI control unit (N3/9) (on model 221 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.
Function sequence for shutting off the stationary heater (STH) (with code (228) Stationary heater)
The STH is shut off automatically after a crash event has occurred. The crash signal is transmitted by the restraint systems control unit via the chassis CAN to the central gateway control unit. This routes the signal via the interior CAN to the stationary heater control unit (A6n1) (model 216) or to the stationary heater or heater booster control unit (A6n1) (model 221), which triggers the shutoff of the stationary heater.
Detailed information is available in the separate function description "Stationary heater (STH)".
Function sequence for automatic emergency call (with code (359) TELE AID emergency call system)
An emergency call is made automatically after a crash event has occurred. The crash signal is transmitted by the restraint systems control unit via the chassis CAN to the central gateway control unit. This sends the signal via diagnostic CAN (CAN D) to the emergency call system control unit (N123/4), which triggers the automatic emergency call.
The crash signal is also transmitted via a discrete line from the restraint systems control unit to the emergency call system control unit
Detailed information is available in the separate function description "Emergency call system".
| Electrical function schematic for deployment of supplemental restraint system (SRS) | Model 216 | PE91.60-P-2053-97CAA | |
| Model 221 | PE91.60-P-2053-97SAA | ||
| Component description for instrument cluster | A1 Model 216.3, model 221 (except 221.095/195) |
GF54.30-P-6000LE | |
| Model 221.095/195 | GF54.30-P-6000LEH | ||
| STH control unit, component description | A6n1 With code (228) Stationary heater |
GF83.70-P-4200LE | |
| Component description for restraint systems control unit | N2/7 | GF91.60-P-4048LE | |
| Component description for Weight Sensing System (WSS) control unit | N2/13 Model 221 with code (494) USA version up to 31.8.08 |
GF91.60-P-4046LEU | |
| Component description for ME-SFI [ME] control unit | N3/10 With engine 156 |
GF07.61-P-6000MAS | |
| With engine 157, 278 | GF07.61-P-6000MMC | ||
| Component description for front SAM control unit with fuse and relay module | N10/1 | GF54.21-P-6070LE | |
| Component description for rear SAM control unit with fuse and relay module | N10/2 | GF54.21-P-6030LE | |
| Rear control unit, component description | N22/6 Model 216 |
GF54.21-P-4134LA | |
| Left front seat control unit, component description | N32/1 | GF91.29-P-5230LE | |
| Right front seat control unit, component description | N32/2 | GF91.29-P-5240LE | |
| Component description for ESP control unit | N47-5 Model 216.3, 221 (except 221.095/195) |
GF42.45-P-5118LE | |
| Component description for left door control unit | N69/1 Model 216 |
GF72.29-P-4124LA | |
| Component description for right door control unit | N69/2 Model 216 |
GF72.29-P-4128LA | |
| Component description for overhead control panel control unit | N70 | GF82.20-P-5216LE | |
| Component description for central gateway control unit | N93 | GF54.21-P-4170LE | |
| Component description for Weight Sensing System (WSS) control unit | N110 Model 216 with code (494) USA version, model 221 with code (494) USA version as of 1.9.08 |
GF91.60-P-4069LAU | |
| Component description for emergency call system control unit | N123/4 With code (359) TELE AID emergency call system |
GF82.95-P-3212LEU |