4. System description · The wheel speeds, steering angle, vehicle speed, transverse accelerationand the brake pressure in the

911 Carrera 4 (996) PSM diagnosis 4. System description The wheel speeds, steering angle, vehicle speed, transverse accelerationand the brake pressure in the brake master cylinder are measuredand processed in the PSM control module. The control module is connected with the control modules of the engine -and for Tiptronic with the transmission management- by means of a CANdata bus. These digital line connectionsallow rapid data exchange betweenthe PSM, DME and Tiptronic control modules. The control module is constantlysuppliedwith current data about the enginetorque, accelerator pedal position and transmissionratio (for Tiptronic), The rate-of-turnand trans- verse acceleration sensors detect the forces which act to turn the vehicle around its centre of gravity. The longitudinaland transverse forces on the wheelscan be calculatedfrom the value measurements listed. If these values exceed certain control thresholds,the control module triggers the appropriate sole- noid valves and the return pump in the hydraulic unit in order to specificallyapply defined brake pressure to one wheel or to severalwheels. 4503 Diagnosis/troubleshooting PSM 45 -D 71