Preventive Occupant Protection System, Basic Function - GF91.40-P-9900A

Model All (CAR) 

Overview 

This document contains information on:

• General 
• Function requirements 
• Function 
  • Preventive occupant protection measures 
  • Reversible emergency tensioning retraction 
  • Seat adjustment (vehicles with seat adjustment with memory function) 
  • Close sliding sunroof (vehicles with sliding sunroof or panoramic sliding sunroof) 
  • Close side window, leaving a small gap 
  • PRE-SAFE® Sound for activation of a reflex in the inner ear as biomechanical hearing protection 

General 

The approach of the preventive occupant protection system is to recognize potential risks of accident at their origin. For this purpose, various sensory capabilities are used, not least through the networking with driver assistance systems. In hazard situations, different actuators are actuated according to the situation in order to deploy their protective effect before the actual impact.

If the accident fails to happen, the fully reversible systems can be restored to their default positions and are immediately ready for operation again.

Depending on the equipment installed, the preventive occupant protection system can be extended by the following functions:

• Rear collision warning system (vehicles with Driving Assistance Package)
• Preventive occupant protection system for side impacts (vehicles with PRE-SAFE® Impulse Side)
• Measures when detecting a high-voltage battery thermal event (hybrid vehicles or electric vehicles)
• Measures for recognition of a thermal event of 48V battery (vehicles with 48V technology)

Function requirements 

• Terminal 15 ON

Function 

The preventive occupant protection system defines the driving state based on the following parameters:

• Vehicle deceleration
• Wheel speeds
• Natural dynamics of the vehicle (yaw rate, lateral acceleration)
• Steering angle
• Thermal event of high-voltage battery (hybrid vehicles or electric vehicles)

The following situations are classified as accident-critical:

• Emergency braking: Rapid brake pedal operation (startle response).
• Maximum full-stop braking: The driver's deceleration request is significantly greater than the physically possible vehicle deceleration (e.g. aquaplaning, ice or snow). Strong interventions of the anti-lock braking system (ABS).
• Severe oversteer: Swerving of rear end combined with strong ESP® stabilization interventions.
• Severe understeer: The vehicle pushes over the front wheels. Strong ESP® stabilization interventions.
• Side wind stabilization: Drifting from the lane, combined with considerable amount of ESP® stabilization intervention.
• Critical steering movements: Rapid steering at high speeds (startle response by the driver combined with excessive stress).
• Secondary accident: The occurrence of another crash after an accident.
• Vehicles with radar-assisted traffic area monitoring:
  • Strong brake force boosting by the Active Brake Assist: Risk of collision in linear or cross traffic.
  • Autonomous brake application by the Active Brake Assist: Risk of collision in linear traffic.
  • Autonomous course correction by the Blind Spot Assist: Course-correcting brake application when there is a risk of collision with vehicles to the side.
  • Collision object detection at front/rear/side: Detection of an imminent collision.

The activation threshold for the preventive occupant protection measures is modified according to the following variables:

• ESP® mode
• Drive program (vehicles with automatic transmission)

Preventive occupant protection measures 

The preventive occupant protection system activates the following measures for occupant protection in critical driving situations:

• Reversible seat belt tensioning (driver and front passenger)
• Seat adjustment (vehicles with seat adjustment with memory function)
  • Position front passenger seat
  • Adjust seat contour of multicontour seat (vehicles with multicontour seats)
• Close sliding sunroof (vehicles with sliding sunroof or panoramic sliding sunroof)
• Close side window, leaving a small gap
• PRE-SAFE® Sound for activation of a reflex in the inner ear as biomechanical hearing protection

All measures are deactivated as soon as the prevailing situation is no longer evaluated as critical.

Reversible emergency tensioning retraction 

The reversible emergency tensioning retraction reduces the amount of seat belt slack by tensioning the front seat belts. The driver and front passenger are held better in the seats. Depending on the situation, the seat belt is tightened with varying force and speed.

As soon as the seat belt is fastened, the belt adjuster reduces the existing slack by tightening the seat belts. The function is available for the front seats. It can be switched on and off via the vehicle settings controls.

Seat adjustment (vehicles with seat adjustment with memory function) 

To enable the best possible occupant protection, the preventive occupant protection system requests adjustment of the front passenger seat and, in the case of multicontour seats (vehicles with multicontour seats), adjustment of the seat contour. Priority applies to manual adjustment. In other words:

• If a manual seat adjustment is taking place when the PRE-SAFE® situation occurs, the seat follows this manual adjustment request. As soon as the seat adjustment switch is released, the seat follows the PRE-SAFE® request.
• Inversely, manual operation of the seat adjustment switch interrupts the PRE-SAFE® adjustment, and the seat remains stationary.

The following settings can be made:

• The front passenger seat is moved to a more favorable position in terms of safety. Depending on the current seat position, the following adjustments are made:
  • Backrest inclination
  • Seat fore/aft position
  • Seat cushion inclination
• The side inserts in the multicontour seats (vehicles with multicontour seats) are inflated. This fixes the occupant in the center of the seat.
• The air cushions of the lumbar supports (vehicles with multicontour seat) are deflated. The occupant thus sits lower in the seat.

The adjustments are completed when the target seat position is reached. After completion or cancellation of the measure, the front passenger seat remains in the held position.

Close sliding sunroof (vehicles with sliding sunroof or panoramic sliding sunroof) 

The sliding sunroof is closed completely by the preventive occupant protection system if it was open in the tilt position previously. If the sliding sunroof was previously open in the sliding direction, it is closed leaving a small gap. If the vehicle rolls over, for example, this makes it less likely that objects can enter the vehicle interior and that limbs of the occupants can protrude from the vehicle. After completion or cancellation of the measure, the sliding sunroof remains in the held position.

Close side window, leaving a small gap 

The side windows are closed, provided that there is sufficient time, leaving a gap of approx. 50 mm. This prevents objects from entering the vehicle and limbs from protruding from the vehicle. Furthermore, it allows the smoke particles arising from the activation of the restraint equipment to disperse quickly. Any active automatic sequence in the opening direction is aborted. However, manual adjustment (first notch of the switch) has priority and is carried out. When the side windows are closing, the automatic reversing function is active. If required, the closing process is reversed. After completion or cancellation of the measure, the side windows remain in the held position.

PRE-SAFE® Sound for activation of a reflex in the inner ear as biomechanical hearing protection 

During an accident, noises with high sound-pressure levels can be generated that damage the hearing. The output of a noise signal via the speaker system shortly before a possible accident prepares the occupants' hearing for the expected accident noise. The noise signal can trigger a natural reflex in the vehicle occupants that protects the eardrum against high sound pressure levels. This can reduce the harm to the occupants' hearing.

	Function schematics
	Trigger preventive occupant protection system, function schematic	Model 118, 177, 243, 247	PE91.40-P-2500-97A
		Model 167, 293	PE91.40-P-2500-97B
		Model 223	PE91.40-P-2500-97C
		Model 213, 238, 257, 290 as of model year 2021	PE91.40-P-2500-97D
		Model 206, 254	PE91.40-P-2500-97E
		Model 295, 296, 297	PE91.40-P-2500-97F
		Model 232	PE91.40-P-2500-97G
	Further basic functions
	Rear end collision warning system, basic function		GF91.40-P-1002A
	Side impact preventive occupant protection system, basic function	Model all (CAR) with code 292 (PRE-SAFE® Impulse Side)	GF91.40-P-1005A
	Traffic area monitoring, basic function		GF54.71-P-1000A
	Power window assembly, basic function		GF67.39-P-9900A
	Open/close sliding sunroof, basic function	Model all (CAR) with code 413 (Panoramic sliding sunroof/ glass roof) Model all (CAR) with code 414 (Electric sunroof, glass version	GF77.20-P-9901A
	Speaker system, basic function		GF82.62-P-9900A
	Front seat electrical seat adjustment, basic function		GF91.10-P-9900A
	Multicontour seat, basic function		GF91.25-P-9900A
	Electronic Stability Program control unit, basic function		GF42.45-P-9890A
	Reversible belt tensioner, basic function		GF91.40-P-9890A