PRE-SAFE function - GF91.40-P-0001GM
MODEL 164.1 as of model year 2009 /YoM 08 model refinement package
MODEL 164.8, 251.0 /1 as of model year 2009 /YoM 08
Function requirements, general
- Circuit 15 ON
- Vehicle speed v > 30 km/h
The EZS control unit (N73) makes the circuit status circuit 15 available via the interior CAN (CAN B).
If the speed drops below v = 30 km/h during a PRE-SAFE situation, all PRE-SAFE functions remain active until the speed has dropped below v = 3 km/h.
General information about the PRE-SAFE system
The PRE-SAFE system is activated in critical driving states, e.g. in a potential accident situation. The goal is to create the most favorable conditions possible for the occupants during the accident by activating the functions before the actual impact.
As well as other input factors, it is mainly the data from the ESP control unit (N47-5) (except model 164.195) or the regenerative braking system control unit (N30/6) (with model 164.195) that is used to trigger PRE-SAFE. The PRE-SAFE system is controlled from the left front reversible emergency tensioning retractor (A76) and the right front reversible emergency tensioning retractor (A76/1)
The PRE-SAFE system consists of the following subfunctions:
- Function sequence for registering of activation criteria
- Function sequence for Electronic Stability Program (ESP) switched to passive
- Function sequence for reversible tensioning retraction
- Function sequence for adjustment of front passenger seat (with code (242) Electrically adjustable front passenger seat with memory)
- Function sequence for closing all door windows
- Function sequence for automatic closing of tilting/sliding roof [SHD] (with code (414) Power glass tilting/sliding sunroof) or automatic closing of panoramic sliding sunroof (for model 251 with code (413) Panoramic sliding sunroof with top sliding sunroof)
- Function sequence for display of fault messages
- Function sequence for ending PRE-SAFE
Function sequence for registering of activation criteria
The recording of the activation criteria comprises the following subfunctions:
- Function sequence for recording vehicle longitudinal dynamics
- Function sequence for recording vehicle lateral dynamics
Function sequence for recording vehicle longitudinal dynamics
The operating speed of the brake pedal is recorded by the ESP control unit or the regenerative braking system control unit. It is thus possible to detect if the driver presses the brake pedal very quickly (e.g. startled reaction). The information "Brake Assist System (BAS) active" is made available to the reversible emergency tensioning retractors by the ESP control unit or the regenerative braking system control unit via the engine compartment CAN (CAN C).
Function sequence for recording vehicle lateral dynamics
- Excessive oversteer:
- A large rear axle slip angle that can no longer be stabilized even with the Electronic Stability Program
- Excessive understeer:
- A large, front-axle slip angle pending for an extended period, which can no longer be stabilized by 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 take place until after speeds of v >
140 km/h have been reached. The activation characteristics become more sensitive with increasing speeds
Function sequence for Electronic Stability Program switched to passive
The triggering threshold for the PRE-SAFE functions is raised if the ESP is manually switched to passive through the ESP OFF switch (N72/1s1) in the upper control panel control unit (N72/1). The upper control panel control unit transmits the signal over the interior CAN to the central gateway control unit (N93). The central gateway control unit transmits the signal via the engine compartment CAN to the ESP control unit or the regenerative braking system control unit.
Additional function requirements for reversible emergency tensioning retraction for driver and front passenger
- Each seat belt inserted into seat belt buckle
- Front passenger seat occupied recognized