Active Brake Assist Controller Unit, Component Description - GF30.30-P-3222RFM

Model 205 

as of model year 2019 

with code 258 (Active Brake Assist System) 

Model 253 (except 253.99) 

as of model year 2020 

with code 258 (Active Brake Assist System) 

Shown on model 205.0 with code P23 (EXCLUSIVE Exterior) 

Fig 1: Active Brake Assist Controller Unit Components Location - Model 205 with code(s) 258 and P23

Courtesy of MERCEDES-BENZ USA

Except code P23 (EXCLUSIVE Exterior), shown on model 205.3 with code P76 (standard equipment exterior) 

Courtesy of MERCEDES-BENZ USA

Location 

With code P23 (EXCLUSIVE Exterior), the Active Brake Assist controller unit is located to the front right behind the bumper.

Except code P23 (EXCLUSIVE Exterior), the Active Brake Assist controller unit is located to the front center in front of the cooler.

Tasks 

The Active Brake Assistant controller unit detects obstacles and vehicles moving immediately ahead and warns the driver about a possible collision.

If the Active Brake Assistant controller unit detects a risk of collision, it initiates autonomous brake application.

This results in the following tasks for the Active Brake Assistant controller unit:

• Reading in input factors 
• Evaluation of input factors 
• Transmission of initial parameters 

Reading in input factors 

The Active Brake Assistant controller unit receives the following input factors via periphery CAN (CAN PER), among other things:

• Engine running or drive train operational.
• Terminal status of terminal 15
• Wheel speed and wheel rotation direction
• Acceleration/yaw rate
• ESP® status
• Steering wheel angle and steering wheel velocity
• Accelerator pedal position
• Brake pedal position
• Switch position of combination switch (S4)
• Driver request via menu settings in the instrument cluster (A1)

The resulting functions are described in the respective function descriptions (see also the appropriate block diagram or function schematic).

Evaluation of input factors 

The input factors are evaluated by the microprocessor and the corresponding assembly parts are actuated.

Transmission of initial parameters 

The Active Brake Assistant controller unit sends the following initial parameters via periphery CAN, among other things:

• Requests to output visual warning messages and warning tones via the instrument cluster
• Request to initiate PRE-SAFE® measures (with code 299 (PRE-SAFE® system))
• Request to increase the braking torque
• Request for torque reduction

The functions that use these signals are described in the individual function descriptions (see the appropriate block diagram or function schematic).

Structure 

The Active Brake Assistant controller unit contains the following assembly parts:

• Radar sensor
• Control unit

Properties of the radar sensor:

• Detection angle of radar sensor: s = 0 up to 160 m with a detection angle of ∠ = 45°
• 77 GHz radar sensor operating on the pulse Doppler principle for independent measurement of distance and speed

The Active Brake Assist controller unit must be newly adjusted after being replaced (e.g. after an accident repair) via the integrated "service adjustment mode."