SAAB WIS ONLINE

Brake pressure sensor

Brake pressure sensor


A pressure sensor in the hydraulic unit monitors the incoming brake pressure from the master cylinder in the primary brake circuit. The pressure sensor sends a voltage to the control module that is proportional to the pressure produced when the driver depresses the brake pedal.

The pressure sensor consists of a membrane and a piezoelectric crystal.


Pin Test reading Description
1



System ground

2

0-5 V, equivalent to 0-250 bar

Output signal

3

+5 V

Power supply from control module



Function


When the driver depresses the brake pedal, the brake fluid is forced into the pressure duct (1). The steel membrane (2) is depressed and acts on a piezoelectric unit (3). The distribution of charge in the piezoelectric unit thus changes. This signal is amplified in the electric circuit (4) and sent to the ESP system.

Diagnostics

In the event of a faulty signal from the pressure sensor, a short circuit or open circuit a DTC is generated in the ESP control module. The following warning lamps come on: ABS, foot brake, ESP OFF and central warning lamp.

Diagnostic help

The voltage from the brake pressure sensor can be read using the diagnostic tool. The value should be 0 V when the pump is stationary and the brake pedal released.