4. Speed sensors 4 -Booster pump · Installationposition: on the front and rear wheel

911 Carrera (996) PSM diagnosis 4. Speed sensors 4 -Booster pump Installationposition: on the front and rear wheel carriers. 5 -Hydraulic unit with control module The speed sensors are conventionalpassive sensors with a pulse wheel. They supplythe Booster pumpPSM control module with information about the current wheel speed. Installation position: Carrera 4, on the left side of the front end. Carrera 2, on the right side of the front end. 5. Brake system Installation position: in the front end The brake master cylinderJthe vacuum brake booster Jthe hydraulic unit and the booster pump are installed in the front end. The brake master cylinder is a tandem brake master cylinder with modified central valve. The figure shows configuration of the Carrera 4. 4_230_99 A sufficientlyfast pressure increase in the wheel brakes is important for perfect control of the driving dynamics. In order to guaranteea secure flow capacity of the return pump across the entire temperature range, the booster pump is switched in the case of driving dynamics control and an admissionpressure of up to 20 bar is built up in front of the return pumps. 45030002 Effects in the case of failure: 1 -Expansion tank with brake fluid level switch ThePSMfunctionis switchedoff. 2 -Vacuum booster 3 -Brake master cylinder 4503 Diagnosis/troubleshooting PSM System PSM05XX 45 -D 195