Mercedes Benz 216 Brake system Control Unit

As in the S-Class, the CL-Class employs the brake system ADAPTIVE BRAKE with HOLD function and Hill Start Assist.
The functions relevant to comfort and safety include:
• Hill Start Assist
• The HOLD function
• Dry braking
• Precharging
The Hill Start Assist function prevents the vehicle from rolling back on hills (within the physical limits) while the driver changes from the brake pedal to the accelerator.
The function cuts in automatically when stationary whenever the moving-off process occurs above a certain gradient.
In contrast to the HOLD function, the Hill Start Assist function holds the pressure for only approx. 0.7 s when the driver takes his foot off the brake pedal.
If the driver changes to the accelerator pedal before the holding time expires, the brake pressure is reduced in proportion to the drive torque and the gradient.
If the driver does not operate the accelerator pedal after the brake pedal, the brake pressure is dissipated.
The Hill Start Assist is deactivated in the event of a malfunction in the ESP system.
In contrast to the holding function, the vehicle is not held if a system error occurs while the Hill Start Assist is active.
The HOLD function allows the driver to hold the vehicle without having to keep the brake pedal depressed.
The HOLD function can be activated in all gear selector modes with the exception of the "P" mode.
In order to activate the HOLD function the vehicle must be stationary and the brake pedal must briefly be depressed all the way with slightly more force than normal. When the driver takes his foot off the brake pedal, the fixed brake pressure is maintained indefinitely.
A status line in the instrument cluster confirms that it has activated successfully.
The HOLD function is deactivated by:
• Depressing the accelerator pedal
• Depressing the brake pedal again beyond the fixed braking point
• Engaging the electric parking brake or engaging the selector position "P"
When the HOLD function is deactivated, the status line in the instrument cluster goes out.
If a system error occurs while the HOLD function is active, the vehicle is held by the electric parking brake or by selecting "P" mode.
The dry braking function improves the braking effect in wet conditions. Brief, light application of the brakes removes the film of water present on the brake disks in wet conditions.
The rain sensor detects whether such an actuation of the brake system is necessary. This function is activated automatically, without driver intervention.
The precharging function is constantly active and improves the braking effect by applying pressure to the brake linings (precharging), when the driver switches quickly from the accelerator pedal to the brake pedal. This reduces the brake actuation time and reduces the stopping distance required in case of emergency braking.

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