ASR Pressure Build-Up Control Mode
The control process and valve positions shown in the figure relate to the RR brake. If one of the drive wheels tends to spin when starting off or accelerating, the control module introduces the ASR pressure build-up control mode. At the start of ASR control, the switchover solenoid valve (y19) is switched to the "shut-off position" (closed) and the high-pressure/return pump (m1) is actuated. The inlet solenoid valve (y23) is only opened during the pressure build-up phases, and the self-priming high-pressure/return pump (p2) draws brake fluid out of the reservoir via the inlet solenoid valve (y23) and via the master brake cylinder. The pressure limiting valve (minimum 150 bar) integrated in the switchover solenoid valve (y19) serves to limit high pressure.