GF91.60-P-0002TX Supplemental Restraint System (SRS), Function

GF91.60-P-0002TX Supplemental Restraint System (SRS), Function

Entire function
Function requirements
^ The supplemental restraint system (SRS) has to be programmed for the vehicle, dependent upon left-hand or right-hand drive vehicle, equipment programming, and configuration parameters
^ C. 15R On
^ Circuit 15 On

The supplemental restraint system (SRS) provides passive interior protection. The following events can be recorded and distinguished:
^ Head-on collision
^ Rear end collision
^ Side collision
^ Roll-over

In the event of an accident, the appropriate restraint equipment is deployed depending on the severity of the impact and the type of accident that has been recognized:
^ Driver airbag (two-stage)
^ Front passenger airbag (two-stage)
^ Driver/front passenger sidebag
^ Left/right windowbag
^ Driver/front passenger emergency tensioning retractor (up to 31.5.06 (not (United States Of America) or (Japan)) or up to 30.6.06 (only (United States Of America) or (Japan)))
^ Driver/front passenger buckle emergency tensioning retractor (as of 1.6.06 (not (United States Of America) or (Japan)) or as of 1.7.06 (only (United States Of America) or (Japan)))
^ Left/right rear emergency tensioning retractor
^ Driver/front passenger belt force limiter (up to 31.5.06 (not (United States Of America) or (Japan)) or up to 30.6.06 (only (United States Of America) or (Japan)))
^ Right/left rear sidebag (with code (293) Left and right rear sidebag)

Collision detection and ignition time determination
The restraint systems control unit (N2/7) measures the acceleration using the driver-side frontal acceleration sensor (B48/1), the passenger-side frontal acceleration sensor (B48/2), the driver sidebag and windowbag sensor (A53/1) and the front passenger sidebag and windowbag sensor (A54/1), and detects whether the requirements for deploying the relevant restraint equipment have been met.

If a threshold is exceeded the ignition stages for the enabled retention systems are actuated. Actuation is for at least 2 ms. thus ensuring that the corresponding restraint system has been reliably triggered.

The restraint equipment is activated in the event of a crash depending upon the type of accident. A distinction is made between a head-on collision, a rear end collision, a side impact and a rollover, and the relevant restraint equipment is activated accordingly.

System monitoring
The supplemental restraint system (SRS) is constantly monitoring itself and immediately signals any errors to the driver via the multifunction display (A1p13) in the instrument cluster (A1). The airbag indicator and warning lamp (A1e15) in the instrument cluster is also switched on.

When circuit 15R is switched on, the airbag indicator and warning lamp and the automatic child seat recognition airbag OFF indicator lamp (N72/1e1) are switched on. If no error is detected after the self-test, the airbag indicator and warning lamp and the automatic child seat recognition airbag OFF indicator lamp are switched off again after approx. 4 s.

All faults are stored in the nonvolatile memory of the restraint systems control unit. The supplemental restraint system (SRS) has a capacitor in the restraint systems control unit. After a battery disconnection, the entire supplemental restraint system (SRS) is provided with power for at least another 150 ms. The driver-side and passenger-side frontal acceleration sensor is supplied with voltage for at least 30 ms.

Because of errors during a crash, the airbag indicator and warning lamp in the instrument cluster is irreversibly actuated by the restraint systems control unit in the following cases:
^ Immediately after the entry of the 5th collision telegram.
^ By a fault detected in the restraint systems control unit, in the external ignition circuits or the remote sensors.
^ If the instrument cluster detects a break in communication with the restraint systems control unit, the airbag indicator and warning lamp is automatically switched on by the instrument cluster, and a fault is stored in the internal memory. In this case a fault is not written to the restraint systems control unit.

With (United States Of America) in the event of a collision or rollover and the relevant triggering threshold is exceeded, and automatic emergency call is also transmitted by the emergency call system control unit (N123/4).

Front passenger seat occupied recognition sensor (as of 1.6.05 without code (U18) Automatic child seat recognition (ACSR [AKSE]))
The front passenger seat occupied recognition sensor recognizes whether or not the front passenger seat is occupied by a person

In vehicles as of 1.6.07 the information about the front passenger seat occupancy status does not influence the decision whether to deploy the front passenger airbag

Automatic child seat recognition (up to 31.5.05 standard equipment, as of 1.6.05 with code (U18) Automatic child seat recognition (ACSR [AKSE]))
The automatic child seat recognition detects whether the front passenger seat is occupied by a person or a child seat. If the seat is occupied by a child seat with built-in transponder, its direction of installation is also determined.

Weight sensing system (WSS) (with (United States Of America) as of 1.6.06)
The WSS detects whether the front passenger seat is occupied by a person or a child seat.

Seat belt reminder warning
The driver seat belt buckle restraint systems switch (S68/3) and the front passenger seat belt buckle restraint systems switch (S68/4) are read in by the restraint systems control unit and monitor, for output of the seat belt reminder warning via the instrument cluster, whether the seat belts of the driver and front passenger seat have been buckled.

Automatic emergency opening of the central locking (CL)
An additional crash sensor is installed in the rear SAM control unit with fuse and relay module (N10/2)

In the event of a severe deceleration, the emergency opening signal is transmitted from a certain value on. After a brief waiting time, this signal is transmitted by the rear SAM control unit via the Controller Area Network Bus class B (interior) (CAN-B) to the left front door control unit (N69/1), the right front door control unit (N69/2), the left rear door control unit (N69/3) and the right rear door control unit (N69/4), which unlock the doors.

Automatic flasher
In the event of a crash, the hazard warning system is switched on automatically. The restraint systems control unit transmits the crash signal via the CAN-B to the rear SAM control unit, which acts as the flash controller.

Automatic engine shutoff
In the event of a crash, the restraint systems control unit transmits an engine shutoff signal via the CAN-B. This signal is redundantly routed by the EIS [EZS] control unit (N73) and the central gateway control unit (N93) to the ME-SFI [ME] control unit (N3/10) (with gasoline engines) or the CDI control unit (N3/9) (with diesel engines) via the Controller Area Network Bus class C (engine compartment) (CAN-C).

Automatic stationary heater (STH) shutoff (with code (228) Stationary heater)
In the event of a crash, the stationary heater (STH) is automatically shut off by the restraint systems control unit.