Rear Pre-Safe(R), Function - GF30.30-P-0015FG
Model 213
up to model year 2021
with code 253 (Rear impact warning and protection system)
Function requirements, general
- No undervoltage or overvoltage
- Engine running or drivetrain operational
- No trailer recognized (with CODE 550 (Trailer hitch))
The CDI control unit or the ME-SFI [ME] control unit sends the "Engine running" or "Drivetrain operational" signal to the Intelligent Drive control unit via drivetrain CAN, powertrain control unit and chassis FlexRay.
The trailer recognition control unit (with code 550 (Trailer hitch)) sends the "Trailer recognized" status via the interior CAN, electronic ignition lock control unit and chassis FlexRay to the Intelligent Drive control unit.
Rear end PRE-SAFE®, general
The rear end PRE-SAFE® function extends the preventative occupant protection system in dangerous situations associated with following traffic. The rear bumper radar sensor on the outer right and left detect the traffic behind one's own vehicle. The Intelligent Drive control unit analyzes the information provided by the rear bumper radar sensors on the outer right and left to determine the closing speed of and distance to following traffic. Various measures are introduced on this basis that may be able to reduce the consequences of an accident for the vehicle occupants.
The possible measures are shown in chronological order in the following graphic:
The rear end PRE-SAFE® function consists of the following subfunctions:
- Function sequence for vehicle detection and warning about the traffic to the rear (Escalation level t 1 )
- Function sequence for preparing the stationary vehicle for a collision (escalation level t 2 )
- Function sequence for activating the occupant protection measures (escalation level t 3 )
- Function sequence for securing the vehicle after the collision (escalation level t 4 )
Function sequence for vehicle detection and warning about the traffic to the rear (Escalation level t 1 )
If a pulling-up vehicle is detected by the rear bumper radar sensors on the outer right and left and is classified by the Intelligent Drive control unit as accident-critical, the driver of this following vehicle is warned through output of the rear end hazard warning flasher function.
The flashing frequency of the rear turn signal indicator is f = 5 Hz.
Model 213
up to model year 2021
with code 253 (Rear impact warning and protection system)
with code 460 (Canada version)
with code 494 (US version)
The following traffic is not warned by the rear hazard warning flasher function.
Technical implementation
The Intelligent Drive control unit reads in the signals from the rear bumper radar sensors on the outer right and left via the radar CAN, evaluates them and sends the request for outputting a warning via chassis FlexRay, electronic ignition lock control unit and interior CAN to the front SAM control unit. This evaluates the incoming request and activates the function rear end hazard warning flasher.
Additional function requirements for preparing the standing vehicle for a collision (escalation level t 2 )
- Vehicle standing still (v = 0 km/h)
- A braking request is recognized by through actuation of the brake pedal or actuation of the parking brake or engaging the gear range "P"
- The brake request is transmitted from the hold function or the DISTRONIC interval pilot (with code 23P (Driver Assist Package Plus))
- The vehicle is braked top a standstill by the DISTRONIC interval pilot (with code 23P (Driver Assist Package Plus))
The Electronic Stability Program control unit sends the status of the braking system via the chassis FlexRay to the Intelligent Drive control unit.
The Electronic Stability Program control unit reads in the status of the electric parking brake switch directly and sends the status of the electric parking brake switch via chassis FlexRay to the Intelligent Drive control unit.
The fully integrated transmission control unit sends information about the selected gear range via drivetrain CAN, powertrain control unit and chassis FlexRay to the Intelligent Drive control unit.
The Electronic Stability Program control unit calculates the vehicle speed from the wheel speed signals and sends this via the chassis FlexRay to the Intelligent Drive control unit.
Function sequence for preparing the stationary vehicle for a collision (escalation level t 2 )
If the Intelligent Drive control unit registers no or only inadequate deceleration of the approaching vehicle over the closing speed, the vehicle is "firmly braked" by increasing the brake pressure as a preventive measure. The hard braking on the one hand significantly reduces the occupant load (whiplash), while on the other hand serves the protection of other road users. Uncontrolled movements of the vehicle after a rear-end collision that could lead to subsequent collisions are minimized (collision with a vehicle in front, collisions with pedestrians or other road users in situations involving an intersection).
Technical implementation
The Intelligent Drive control unit sends the brake request via chassis FlexRay to the Electronic Stability Program control unit, which then actuates the traction system hydraulic unit accordingly.
Function sequence for activating the occupant protection measures (escalation level t 3 )
If the Intelligent Drive control unit calculates that a rear-end collision is probable using the closing speed of the approaching vehicle, preventive measures designed to provide protection to occupants are initiated. The driver and the front passenger are held in position in their seat in order to optimize the protective effect of the conventional restraint equipment.
Technical implementation
The Electronic Stability Program control unit initiates PRE-SAFE® measures to provide protection to occupants.
Function sequence for securing the vehicle after the collision (escalation level t 4 )
After a rear end collision the brake pressure is maintained for short time.
Technical implementation
The technical implementation of "Maintain brake pressure" corresponds to the technical implementation of the escalation level
After a rear-end collision, the rear end PRE-SAFE® function is no longer available until it is activated using a diagnostic tester.
| Electrical function schematic for PRE-SAFE® rear end | PE30.30-P-2061-97DBA | ||
| Overview of system components for driver assistance systems | GF54.00-P-9998FG |