Adaptive brake (ABR), function - GF42.47-P-0001SX
MODEL 221.0 /1, 216.3 up to Model Year 08 /modification year 07
Function of Adaptive Brake (ABR)
ABR assists the driver in dangerous situations which occur suddenly and thus serves active safety.
ABR contains the following functions:
- Electronic Stability Program (ESP)
- Antilock brake system (ABS)
- Acceleration Slip Regulation (ASR)
- Brake Assist (BAS)
- Electronic brake force distribution (EBV)
- Electronic Traction System (ETS)
as well as additional functions:
- HOLD
- Precharging
- Dry braking
- Hill start assist
- Failed boost function (on engine 275)
- Fading brake support
- Air gap reduction (Airgap)
- Standstill coordinator
- Trailer stabilization
The ESP control unit (N47-5) evaluates the data from the following components to record the current driving situation:
- BAS diaphragm travel sensor (A7/7b1)
- BAS travel differential sensor (A7/7b2) (with engine 275)
- BAS release switch (A7/7s1)
- Yaw rate, lateral and longitudinal acceleration sensor (B24/15)
- Left front rpm sensor (L6/1)
- Right front rpm sensor (L6/2)
- Left rear rpm sensor (L6/3)
- Right rear rpm sensor (L6/4)
- Steering angle sensor (N49)
- Pressure sensors in the traction system hydraulic unit (A7/3)
ABS
ABS prevents the wheels from locking up when braking and as a result maintains the steerability and directional stability and road adhesion during vehicle deceleration.
ASR/ETS
ASR/ETS prevents the driven wheels from spinning when the vehicle is being driven. In addition it causes an improved directional stability and road adhesion with an increased traction potential over the entire vehicle speed range.
ESP
ESP prevents breakaway when the vehicle oversteers or understeers. It ensures that the vehicle does not deviate from the course specified by the driver (within physical limits). Brake forces are produced selectively at the individual wheels to correct any deviations. Furthermore a torque reduction takes place to increase directional stability and road adhesion.
BAS
BAS detects emergency braking situations by means of a rapid brake pedal operation and increases the brake pressure if necessary via the BAS solenoid valve (A7/7y1).
BAS PLUS
BAS Plus increases the brake pressure depending on the speed of the brake pedal operation and the distance of the vehicle driving in front.
EBD (Electronic brake force distribution)
EBV assists the driver in the partial braking area. It prevents overbraking of the rear axle and increases vehicle stability when braking in the curve, by reducing the pressure at the rear wheel on the inside of the curve or increasing it at the front wheel on the outside of the curve as required.
HOLD
HOLD assists the driver when starting off on a hill or when waiting in traffic. HOLD is activated by briskly continuing to depress the brake pedal at a standstill. The adjusted brake pressure is maintained until the driver depresses the brake pedal again rapidly or starts off.
With
and
the additional HOLD function is deactivated by coding in the ESP control unit. This takes place by the coding information of the central gateway control unit (N93).
Precharging
Precharging already builds up brake pressure when the accelerator pedal sensor (B37) is released suddenly in order to reduce the response time for a brake application which possibly occurs subsequently (e.g. through BAS).
Dry braking
Dry braking assists the performance of the brake in the wet. The water film is wiped off the brake disk by applying the brake linings in cycles. This improves the response time of the brake.
Hill start assist
Hill start assist prevents the vehicle from rolling back when starting off on a hill during the time it takes for the driver to move his foot from the brake pedal to the accelerator pedal. For this the brake pressure applied by the driver is maintained for a period of 0.8 to 1.5 s by the traction system hydraulic unit and switched off by a suitably large starting off torque.
Failed boost function
The failed boost function serves to ensure a sufficiently high brake pressure level in the system with a shortage of brake boost through the BAS brake booster (A7/7).
Fading brake support
Fading brake support assists the driver when the brake is overheated and thus the brake force is reduced. With extreme overheating a message can appear in the multifunction display (A1p13) of the instrument cluster (A1).
Air gap reduction (Airgap)
Airgap reduces the air gap between the brake disk in order to possibly accelerate the following ASR or ESP pressure buildups.
Standstill coordinator
When the assistance systems are activated such as HOLD and an unclear driver status the standstill coordinator requests the changeover of the vehicle into a secured condition.
Trailer stabilization
The trailer stabilization reduces any vehicle combination instability which may occur.
Function statuses
The function scope can vary depending on the signals received. The following table represents the function shutdown due to component failure or defect.
| Function shutoff | Component failure | |||||||
|---|---|---|---|---|---|---|---|---|
| Steering angle/turn rate sensor | BAS solenoid valve | CAN | Position sensor | Release switch | Pressure sensors of the traction system hydraulic unit | 1 rpm sensor | more than 1 rpm sensor | |
| ESP/BAS | X | X | X | X | X | X | X | X |
| ASR/ETS | X | X | X | X | X | X | ||
| ABS | X | X | ||||||
| EBD (Electronic brake force distribution) | X | |||||||
System faults
The driver is informed about the system condition or about faults by messages in the multifunction display or by the lighting up of the ABS indicator lamp (A1e17), the ESP warning lamp (A1e41) or the ESP indicator lamp (A1e42) in the instrument cluster.
The status of the brake fluid indicator switch (S11) is read in by the front SAM control unit with fuse and relay module (N10/1) and transmitted to the central gateway control unit via the interior CAN. The central gateway control unit transmits the information about the chassis CAN to the ESP control unit. When the brake fluid level is too low the driver is informed via the brake fluid warning lamp (A1e7).
In the event of a failure of the ESP control unit a basic brake function without ABS is always available.
Stop lamp actuation
The stop lamps light up during a brake application.
These are actuated by the rear SAM control unit with fuse and relay module (N10/2). The ESP control unit transmits discreet signal and a CAN signal for stop lamp actuation to the rear SAM control unit. The CAN-signal is routed from the central gateway control unit from the chassis CAN on the interior CAN to the rear SAM control unit.
| Adaptive Brake (ABR) location of components | GF42.47-P-0001-02SX |
| Adaptive Brake (ABR) block diagram | GF42.47-P-0001-03SX |
| Brake assistant (BAS), function | GF42.31-P-0001SX |
| Electronic stability program (ESP) function | GF42.45-P-0001SX |
| Additional functions, Adaptive Brake (ABR), function | GF42.47-P-2000SX |