ESP regulation and brake application: Function

When the ESP operates, the control module starts the return pump, which then runs for the entire modulation cycle. At the same time, the pressure relief valve is shut to allow a build-up of pressure. The pressure increase valve is opened to supply the pump with brake fluid.

The control module closes the pressure increase valve when a preset pressure is reached. The pressure is then regulated by

• opening the pressure increase valve to increase the pressure
• closing the pressure increase valve and pressure relief valve for pressure holding.
• opening the pressure relief valve to lower the pressure

Each wheel is controlled by closing the inlet and outlet valves for that wheel. Excess brake fluid that causes the pressure relief valve to open is returned to the master cylinder.

The pressure increase valve on the wheel which is spinning will open. This causes an increase in the pressure to the wheel cylinder and the wheel is braked.