Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Active Brake Assist Controller Unit, Component Description - GF30.30-P-3222LFM
Model 217, 222
as of model year 2018
with code 258 (Active Brake Assist System)
Shown on model 222
Location
The Active Brake Assistant controller unit is located in the direction of travel at the rear right to the front bumper.
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 drivetrain 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 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 optical and acoustic warning messages in instrument cluster
- Requirements for initiating PRE-SAFE® measures
- Request to increase the braking torque
- Request for torque reduction
The functions that use these signals are described in the individual function descriptions (see 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°
- 76 GHz radar sensor operating on the pulse Doppler principle for independent measurement of distance and speed
The Active Brake Assistant controller unit must be newly adjusted after exchange (e.g. after an accident repair) using the integrated "service adjustment mode".
| Wiring diagram for Active Brake Assist controller unit | PE30.30-P-2108-97SEA |
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
Rather have a pro handle this?
A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.
No obligation. See pricing before you book.