Supplemental restraint system (SRS), function - GF91.60-P-0002T: Notes

MODEL 211.0 /2 

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 is used for passive occupant protection. The following events can be recorded and distinguished:

• Head-on collision
• Rear end collision
• Side collisions
• Roll-over

If an accident occurs, the relevant restraint equipment is activated 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 or ) or up to 30.6.06 (only or ))
• Driver/front passenger buckle emergency tensioning retractor (as of 1.6.06 (not or ) or as of 1.7.06 (only or ))
• Left/right rear emergency tensioning retractor
• Driver/front passenger belt force limiter (up to 31.5.06 (not or ) or up to 30.6.06 (only or ))
• Left/right 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 frontal acceleration sensor (B48/1), passenger-side frontal acceleration sensor (B48/2), driver sidebag and windowbag sensor (A53/1) and front passenger sidebag and windowbag sensor (A54/1) to check, whether the requirements for the activation of the relevant restraint equipment are being 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 systems are activated in the event of a crash depending upon the type of accident. A distinction is made between head-on collision, rear end collision, side impact, and rollover, and the particular restraint systems are activated accordingly.

System monitoring 

The supplemental restraint system continuously monitors itself and signals faults to the driver immediately 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 restraint systems control unit has a capacitor. After a battery disconnection, the entire supplemental restraint system is provided with power for at least another 150 ms. The frontal acceleration sensors are 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 crash telegram.
• By a fault detected in the restraint systems control unit, in the external ignition circuits or the external 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, no error is entered in the restraint systems control unit

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

Front passenger seat occupied recognition sensor (not with and 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.

On vehicles as of 1.6.07, the occupation status information for the front passenger seat does not have any influence on the decision of whether to activate the front passenger airbag.

Automatic child seat recognition (up to 18.2.04 with  , up to 31.5.05 without  , as of 1.6.05 with code (U18) Automatic child seat recognition (ACSR [AKSE])) 

The automatic child seat recognition recognizes, whether or not the front passenger seat is occupied by a person or by a child seat. For a child seat with installed transponder, the system also detects the direction of installation.

WSS (Weight Sensing System) (with as of 19.2.04) 

The seat occupied and child seat recognition is implemented by the weight sensing system (WSS).

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 whether the seat belts on the driver and front passenger seat have been buckled. The seat belt reminder warning is output via the instrument cluster.

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 prompt the doors to be unlocked.

Automatic hazard warning flashing 

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

Automatic engine shutoff 

In the event of a crash, the restraint systems control unit transmits a signal to switch off the engine via CAN-B. This signal is routed redundantly 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 is automatically shut off by the restraint systems control unit.

	Supplemental restraint system (SRS), location of components		GF91.60-P-0002-01T
	Supplemental restraint system (SRS), component networking		GF91.60-P-0002-02T
	Supplemental restraint system (SRS), block diagram		GF91.60-P-0002-03T
	Passenger-side seat occupied recognition function	Without code (494) USA version or as of 1.6.05 without code (U18) Automatic child seat recognition (ACSR [AKSE])	GF91.60-P-1100T
		Up to 18.2.04 with code (494) USA version and up to 31.5.05 without code (494) USA version and as of 1.6.05 with code (U18) Automatic child seat recognition (ACSR [AKSE])	GF91.60-P-1100TA
		As of 19.2.04 with code (494) USA version	GF91.60-P-1100TB
	Head-on collision, function		GF91.60-P-2006T
	Rear end collision, function		GF91.60-P-2004T
	Side impact, function		GF91.60-P-2005T
	Rollover process function		GF91.60-P-2007T