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Additional functions, adaptive brake (ABR), function - GF42.47-P-2000SX

MODEL 221.0 /1, 216.3 up to Model Year 8 

The following additional functions are integrated in the Adaptive Brake (ABR) and are coordinated by the ESP control unit (N47-5):

Additional function 

HOLD 

HOLD makes life easier for the driver optionally:

IMPORTANT With USA ONLY and CANADA ONLY 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).

Function description of HOLD 

When the vehicle is at a standstill HOLD can be switched on by actuating the brake pedal. The actuation of the brake pedal is detected via the BAS diaphragm travel sensor (A7/7b1). The vehicle is then held in position without any further actuation of the brake pedal. The braking effect is canceled when starting off by pressing the accelerator, via the accelerator pedal sensor (B37).

Switching on HOLD 

HOLD can be switched on when

Actuate the brake pedal, then depress the brake pedal briskly again until the message "HOLD" appears in the multifunction display (A1p13). The vehicle is held automatically when the brake pedal is released afterwards.

Switching off HOLD 

HOLD is switched off automatically when

Driver status 

A belt tongue inserted into the seat belt buckle or shifting out of position "P" when the driver door is closed is interpreted as the presence of the driver. When the driver door is open and a belt tongue is not inserted into the seat belt buckle the driver status is not clear and the driver is thus presumed absent. HOLD is not activated when the driver status is not clear.

The status of the seat belt buckle is detected by the restraint systems control unit (N2/7) and the driver seat belt buckle and seat belt warning switch (S68/1). The opening of the driver door on model 216 is detected by the left door control unit (N69/1) and the left rotary tumbler switch (A85s1) and in model 221 by the left front door control unit and the left front rotary tumbler switch (A85s1).

Additional function 

Precharging 

The function is permanently active and assists the performance of the brake system by already applying the brake linings (precharging) when the accelerator pedal sensor is released. As a result the response time of the brake is reduced and the stopping distance reduced during emergency stops.

Function description of precharging 

To reduce the response time during panic braking the air gap of the wheel brake system is already overcome when the accelerator pedal sensor is overcome and the brake linings are applied. If the driver subsequently depresses the brake pedal, a spontaneous braking effect is achieved and thus the stopping distance is reduced. In the process the release gradient of the accelerator pedal sensor is used to detect the rapid braking requirement. The precharging process is terminated after a short time if the driver does not apply the brake.

Determination of the triggering threshold for precharging 

If the boundary conditions are met, the associated release gradient is determined each time the accelerator pedal sensor is released completely. The triggering threshold depends on the pedal travel. With small pedal travels before the pedal is released a smaller pedal release gradient is needed in order to activate precharging, than with large pedal travels before the pedal is released.

Precharging is not active when: 

Additional function 

Dry braking 

The function is permanently active and assists the performance of the brake system in the wet. The response time of the brake is reduced by cyclical dry braking of the brake disks.

Function description of dry braking 

Dry braking is activated as soon as the windshield wiper leaves its basic position. Dry braking itself is only carried out at the front axle for a few seconds with a very small brake pressure (< 1 bar).

Hill start assist 

In the case of starting off uphill (longitudinal gradient) when changing from the brake to the accelerator pedal sensor a delayed depressurization is carried out in the brake system in order to prevent the vehicle rolling back unintentionally.

A longitudinal gradient is detected by the ESP control unit via the turn rate, lateral and longitudinal acceleration sensor (B24/15)

Hill start assist is not active when

Additional function 

Failed boost function 

In combination with signals from the BAS travel differential sensor (A7/7b2) (only with engine 275) the failed boot function serves to ensure a sufficiently high brake pressure level in the system in the event of a shortage of brake boost through the BAS brake booster (A7/7).

Function description of failed boost function 

If during a brake application by the driver it is detected by the BAS travel differential sensor and the ESP control unit that the BAS brake booster does not provide adequate driver assistance, then failed boost ensures driver assistance by hydraulic brake boost.

Additional function 

Fading brake support 

The fading brake support function serves to provide additional driver assistance when the brake system is hot in order to achieve the best possible deceleration in this operating case as well. In the event of a particularly severe heating up an information message is shown in the multifunction display of the instrument cluster (A1).

Function description of fading brake support 

Heating up is determined based on a temperature model of the brake disk. If a particular threshold is exceeded fading is assumed, fading brake support becomes active. In addition this function can also be activated by the comparison of the brake pressure level with the actual deceleration or by the direct request through the antilock brake system (ABS).

Additional function 

Air gap reduction (Airgap) 

Airgap reduces the air gap between the brake disk and lining in order to speed up any subsequent brake applications through ASR or ESP.

Additional function 

Standstill coordinator 

When the support systems are active when the vehicle is stationary the standstill coordinator promotes the actuation of the electric parking brake (EFB) or shifting into position "P" by the Intelligent servo module for DIRECT SELECT (A80). This changes over the vehicle into a secured condition.

The following event lead to actuation of the electric parking brake controller unit (A13):

The following events lead to actuation of the EFB and the

Intelligent servo module for DIRECT SELECT:

Additional function 

Trailer stabilization 

Trailer stabilization reduces vehicle combination swinging by specific brake interventions in order to stabilize the vehicle and trailer.

Instrument cluster, component description A1
Model 221		 GF54.30-P-6000SX
BAS brake booster, component description A7/7 GF42.31-P-4004SX 
Electric parking brake controller unit, component description A13 GF42.20-P-5000SX 
Intelligent servo module (ISM) component description A80
Model 221 with transmission 722.6		 GF27.19-P-4015SXA
  Model 221 with transmission 722.9 GF27.19-P-4015SX
Yaw rate and lateral acceleration sensor, component description B24/15 GF42.45-P-5120SX 
ESP control unit, component description N47-5 GF42.45-P-5118SX 
Driver-side front door control unit, component description N69/1
Model 216		 GF72.29-P-6000SC
Central gateway control unit, component description N93 GF54.21-P-4170SX
Electric parking brake switch, component description S76/15 GF42.20-P-5001SX 
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