Hydraulic Unit Pressure Sensor

The hydraulic system pressure sensor provides a 0-5 volt linear voltage signal to the Dynamic Stability Control (DSC) III control module. The linear voltage is a proportionate indication of how hard the driver is pressing on the brake pedal. The signal is provided as an additional determination factor for the DSC III control module to monitor the hydraulic pressure present during all phases of operation:

^ No braking
^ Partly Brake
^ Near ABS regulation state

For example: Vehicle is braked very hard, immediate increase in brake circuit pressure causes linear signal voltage to rapidly increase. The control module determines high hydraulic pressure may put the system into wheel lock condition requiring ABS regulation. The control module is aware of impending wheel lock before it detects a change in the wheel speed sensor signals. This all results in a faster response time when the wheels actually begin to lock.

The sensor also provides feedback of a functioning preboost charge pump on a 750L or a functioning charge pump on a 740i/iL and 540A

Depending on the vehicle, the sensor is located as follows:

750iL





- On the charge piston unit

740iL and 540iL





- On the charge pump.

The sensor has three pins:
^ power supply
^ ground
^ 0-5 volt signal