Brake Assist (BAS), function - GF42.31-P-0001F

MODEL 463.243 /244 /246 /247 /249 /250 /254 ## as of 127357 as of 1.9.01, 463.270 /271, 463.309 /322 /323 /332 /333 ## as of 127357 as of 1.9.01 with CODE (BB3) Electronic stability program (ESP) 

MODEL 463.248 ## as of 127357 as of 1.9.01 with CODE (BB3) Electronic stability program (ESP) except CODE (979) Special protected version 

Fig 1: Identifying Brake Assist Function Diagram

Courtesy of MERCEDES-BENZ USA

1. General 
   • The "Brake Assist (BAS)" functionality is integrated as a software module in the ESP and BAS control module (N47-5).
   • The Brake Assist (BAS) is an active safety system.
   • There are two emergency braking situations during which the Brake Assist (BAS) is activated. When activated, the BAS system assists the braking procedure initiated by the driver in such a way as to achieve the maximum possible braking deceleration:
     • Hesitant brake application

       The driver applies insufficient pedal force in the initial braking phase and increases the braking force too slowly.

     • Insufficient brake application

       The force applied to the brake pedal is insufficient during the entire brake application.

   • The system detects an emergency braking situation by the speed at which the driver presses the brake pedal and activates the brake booster to increase the brake force to the maximum possible level.
   • The brake force is increased immediately to the maximum possible level to decelerate the vehicle in an optimum way controlled by the antilock brake system (ABS). The ABS prevents the vehicle wheels from locking up.
   • The BAS assists the ABS in dangerous driving situations by increasing the brake force to the maximum possible level so that the shortest possible brake distance can be achieved without the wheels locking up.
   • Full steerability is maintained even during BAS intervention.
   • If there is an operational problem with the BAS, the system is deactivated and the brake force is no longer boosted by the BAS.
2. Function 
   1. 2.1 Normal mode 
      • In the normal operating mode when the Brake Assist (BAS) is not activated, the brake force is built up in the conventional way, i.e. the force applied to the pedal by the driver is increased proportionally by the brake booster.
   2. 2.2 Operation with BAS intervention
      • If the prerequisites for Brake Assist (BAS) activation occur, the brake force is built up by the BAS system rather than by the driver.