Seat Belt Control Module: Description and Operation

GF91.60-P-4048SX Restraint Systems Control Unit, Component Description

Component Identification:

Location
The restraint systems control unit is located below the COMAND controller unit (A40/3) on the center tunnel.

Task
The restraint systems control unit is used to ensure passive occupant protection. If an accident occurs, the restraint systems control unit deploys the restraint systems. These include the airbag units, the ETR units and the buckle emergency tensioning retractors. The restraint systems control unit has self-monitoring and fault monitoring features. Frontal, rear end, and side impacts are recorded, and a distinction is made between the different types of impact. Roll-overs around the longitudinal vehicle axis can also be detected.

Scope of task
^ Accident detection and ignition time determination
^ Ignition stage deployment
^ Front passenger seat occupancy evaluation
^ Storing of non-volatile crash telegrams
^ Self-test and permanent monitoring of the supplemental restraint system (SRS) and fault display with non-volatile storage of faults and downtimes
^ Fault output via the diagnosis communication
^ Capacitor for the event of a battery disconnection if a collision occurs
^ Power supply of:
- Driver side frontal acceleration sensor (B48/1)
- Passenger-side frontal acceleration sensor (B48/2)
- 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)
- Driver airbag system assistant (B48/5)
- Front passenger airbag system assistant (B48/6)
- Front passenger seat occupied and child seat recognition (B48) (not (United States Of America), standard up to 31.5.07, as of 1.6.07 with code (U18) Automatic child seat recognition (ACSR [AKSE]))

^ System readiness display via chassis CAN to instrument cluster (A1) and upper control panel control unit (N72/1)
^ Evaluation of integrated rollover sensor

^ Support of the automatic seat belt reminder warning via the chassis CAN
^ Output of signal for transmitting an emergency call via the chassis CAN (only (United States Of America))
^ Output of a redundant crash signal to the following control units via discrete lines (as of 1.6.07):
- Rear SAM control unit with fuse and relay module (N10/2)
- ME-SFI control unit (N3/10) with gasoline engine or CDI control unit (N3/9) with diesel engine

Discrete inputs
^ Circuit 31
^ Circuit 30
^ Term. 15R
^ Frontal acceleration sensor
^ Airbag system assist
^ Driver door pressure sensor
^ Front passenger door pressure sensor
^ Rear door pressure sensor
^ Driver seat belt buckle and seat belt warning switch (S68/1)
^ Front passenger seat belt buckle and seat belt warning switch (S68/2)
^ Front passenger seat occupied and child seat recognition sensor (not (United States Of America), standard up to 31.5.07, as of 1.6.07 with code (U18) Automatic child seat recognition (ACSR [AKSE]))
^ Front passenger seat occupied recognition (not (United States Of America), as of 1.6.07 without code (U18) Automatic child seat recognition (ACSR [AKSE]))

Discrete outputs
^ Passenger airbag squib 1 (R12/4)
^ Passenger airbag squib 2 (R12/5)
^ Left rear ETR squib (R12/6)
^ Right rear ETR squib (R12/7)
^ Left rear sidebag squib (R12/11)
^ Right rear sidebag squib (R12/12)
^ Driver airbag squib 1 (R12/13)
^ Driver airbag squib 2 (R12/14)
^ 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)
^ Driver kneebag squib (R12/25) (in model 216 only (United States Of America))
^ Drive buckle ETR squib (R46)
^ Front passenger ETR squib (R46/1)
^ Driver NECK-PRO head restraint solenoid (Y24/12) and front passenger NECK-PRO head restraint solenoid (Y24/13) (with model 221 as of 1.9.06)
^ Digital crash output to emergency call system control unit (N123/4) (only (United States Of America))
^ ME-SFI control unit or CDI control unit (redundant crash signal, as of 1.6.07)
^ Rear SAM control unit with fuse and relay module (redundant crash signal, as of 1.6.07)