Phase 1 Pressure build-up for all four wheels (filling pulse and maintenance of pressure). Driver not braking
Filling pulse At the start of modulation, a filling pulse is produced. This means that the pressure in all wheel cylinders is raised slightly (equal for all four wheels), irrespective of on which wheel the brakes are to be applied. The pump starts, the pressure relief valve closes and the pressure increase valve opens (set time).
The inlet and outlet valves are in their normal position in the valve block, i.e. the inlet valves are open and the outlet valves are closed.
Maintenance of pressure Once the filling pulse has stopped, the inlet valves close to prepare for individual regulation on each wheel.
Wheels on which the ESP system is not going to apply the brakes: The pressure will be maintained with the pressure increase and pressure relief valves on each circuit being shut, as well as the inlet and outlet valves by each wheel. This is so that the system is ready in case braking is required.