Theory Of Operation

The Brake Pressure Sensor is located internally in the Anti-lock Brake System (ABS) Hydraulic Control Unit (HCU). It measures the zero level bias of the primary brake circuit when no brakes are applied and no ABS activation is in effect. The zero level bias can change due to residual brake pressure on the brake circuit or due to a bias on the pressure senor. A zero level bias on the pressure sensor is allowed and normal up to +/-16 bar (no actual pressure but the sensor reports some pressure). However an actual pressure buildup on the brake circuit is not allowed, not normal and must be repaired.