PRE-SAFE function - GF91.40-P-0001T

MODEL 211.0/2 as of 1.6.06 except CODE (494) USA version except CODE (498) Japan version 

MODEL 211.0/2 as of 1.7.06 with CODE (494) USA version with CODE (498) Japan version 

Description 

The PRE-SAFE safety system includes a package with the following functions:

• Reversible motorized seat belt tensioning for the driver and front passenger
• Positioning of front passenger through adjustment of front passenger seat (for code (242) Electrically adjustable front passenger seat with memory)
• Automatic closing of all side windows
• Automatic closing of the tilting/sliding roof (with code (414) Electric glass titling/sliding roof)

The PRE-SAFE safety system is activated in the event of critical drive situations, in other words in a potential accident situation. The goal is to create the most favorable conditions possible for the occupants during the expected accident by activating the functions before the actual impact.

Function requirements 

• Circuit 15 ON
• Vehicle speed > 30 km/h

PRE-SAFE activation 

The ESP control unit (N47-5) actuates the PRE-SAFE functions. The rotational speed, lateral and longitudinal acceleration are monitored and analyzed by the ESP control unit.

PRE-SAFE is activated in the event of the following critical drive situations:

PRE-SAFE longitudinal dynamics 

• Emergency stop:
  • The driver is shocked into pressing down on the brake pedal at high speed
• Secondary brake application as a result of a panic reaction:
  • The vehicle does not decelerate according to the driver's intention due to special weather conditions (ice, snow or aquaplaning). The driver depresses the brake pedal in panic down to the maximum pedal travel
• Powerful targeted braking:
  • The Brake Assist (BAS) introduces powerful targeted braking

PRE-SAFE lateral dynamics 

• Severe oversteer:
  • A large rear axle slip angle, which is beyond the manageable driving physics and which cannot be stabilized with the aid of the Electronic Stability Program (ESP) either
• Severe understeer:
  • A large front axle slip angle that is present for a longer period of time, which is beyond the manageable driving physics and which cannot be stabilized either with the aid of the ESP
• Critical steering movement:
  • Steering movement of the driver, which is probably due to a startle reaction and can lead to instability of the vehicle. Activation does not start until after speeds of > 140 km/h have been reached. The activation characteristics become more sensible with increasing speeds

The following table illustrates, which functions are activated in the event of longitudinal dynamics or lateral dynamics.

Activated PRE-SAFE function	PRE-SAFE longitudinal dynamics	PRE-SAFE lateral dynamics
Reversible emergency tensioning retraction	X	X
Positioning of front passenger seat	X	X
Closing of tilting/sliding roof		X
Closing of side windows		X

Function 

The sequence of the PRE-SAFE activities is coordinated via the so-called PRE-SAFE Master. The PRE-SAFE master is the ESP control unit, which is connected over the Controller Area Network bus Class C (engine compartment) (CAN-C) and the central gateway control unit (N93) to the Controller Area Network bus Class B (interior) (CAN-B). The existing vehicle systems are used to realize the PRE-SAFE function.

Function when the ESP is switched off 

The triggering thresholds for longitudinal and lateral dynamic situations are raised, if the ESP closed-loop control is manually switched off using the ESP OFF switch (N72/1s1) in the upper control panel control unit (N72/1).

Consumer shutoff by PRE-SAFE 

In the event of a PRE-SAFE actuation, the following consumers are switched off by a corresponding signal over CAN-B from the central gateway control unit:

• Blower motor (A32m1)
  • over the AAC [KLA] control and operating unit (N22) (without code (581) Comfort automatic air conditioning) or
  • over the Comfort AAC [KLA] control and operating unit (N22/7) (for code (581) Comfort automatic air conditioning)
• Heated rear window (R1)
  • over the rear SAM control unit with fuse and relay module (N10/2)

Ending the PRE-SAFE functions 

PRE-SAFE is deactivated as soon as a PRE-SAFE longitudinal dynamics situation or lateral dynamics situation is no longer present.

The reversible emergency tensioning retraction is released, as soon as the vehicle acceleration has dropped below a value of approx. 3 m/s² .

The ESP control unit transmits a signal over CAN-C to switch off the PRE-SAFE functions. The signal is transmitted to the involved control units via the central gateway control unit over CAN-B. Adjustment of the front passenger seat is interrupted, insofar as the PRE-SAFE position has not yet been reached.

Closing the side windows and the tilting/sliding roof is not aborted. The automatic closing function continues until the PRE-SAFE position has been reached.

In the event of an impact that is recognized by the restraint systems control unit (N2/7), all adjustments are stopped immediately.

Error messages 

If a fault of the left front reversible emergency tensioning retractor (A76) or the right front reversible emergency tensioning retractor (A76/1) is recognized, it is displayed in the instrument cluster (A1). Faults of other components that are part of PRE-SAFE are not displayed as PRE-SAFE faults.

PRE-SAFE, location of components		GF91.40-P-0001-01T
PRE-SAFE, networking of components		GF91.40-P-0001-02T
PRE-SAFE, block diagram		GF91.40-P-0001-03T
Reversible emergency tensioning retraction, function		GF91.40-P-1000T
Positioning the front passenger seat, function	With code (242) Electrically adjustable front passenger seat with memory	GF91.40-P-1001T
Closing the tilting/sliding roof, function	With code (414) Power glass tilting/sliding roof	GF91.40-P-1003T
Closing the side windows, function		GF91.40-P-1004T
Instrument cluster (IC), location/task	A1	GF54.30-P-3039T
Rear SAM control unit with fuse and relay module, location/task	N10/2 Model 211.0	GF54.21-P-4130T
	Model 211.2	GF54.21-P-4130TA
Control and operating unit for automatic air conditioning, location/task	N22 Without code (581) Comfort automatic air conditioning	GF83.40-P-2180T
Comfort automatic air conditioning control and operating unit, location/task	N22/7 with code (581) Comfort automatic air conditioning	GF83.40-P-2181TT
Upper control panel control unit, location/task/design/function	N72/1
	Model 211.0	GF54.21-P-4105T
	Model 211.2	GF54.21-P-4105TS
Electronic ignition switch control unit, location/task	N73	GF80.57-P-4120T