45 Function of individual components · 1. Control module (ABS 5.3 and ABS / TC 5.3) Note

911 Carrera (996) Anti-Lock Brake System (ABS) 45 Function of individual components 1. Control module (ABS 5.3 and ABS / TC 5.3) Note This unit processes incoming signals and actu- The relays cannot be exchanged. ates the solenoid valves and/or the return pump When replacementis necessary,the complete in the hydraulic unit when wheel slip is excessive hydraulic unit must be replaced. (see also System description). If the ABS or ABSjTC switches off when detecting a system fault, it actuates the warning 3. Fuses light and stores the fault in a non-volatile 3a. A 50-A fuse in the current distributor memory. (Fl / arrow) protects the return pump and the solenoid valves. Note The current distributor is located under the Control module and relay are not supplied indi- instrumentpanel. The fastening points are vidually. In the event of replacement,the com- accessible from the luggage-compartment plete hydraulic unit must be replaced. side. 3b. The 15-Afuse B 9 (fuse holder B / fuse No.9) on the central electrical board 2. Relay protects the control module's electrical supply The solenoid valve relay is actuated by the (ABSand ABSjTC). control module (closes) as soon as the control The arrow points to fuse holder B (field 2). module receives voltage from the generator (0+ / terminal 61). On vehicles with Traction Control (TC),the As soon as the relay has closed (picked up), 15-Afuse B 2/1 (fuse holder B / fuse battery + (terminal 30) is applied to the valve No.1) on the central electrical board coils of all solenoid valves of the hydraulic unit. protects the supplyto the "TC OFF"rocker switch (switch for switching driving-stability If the ABS or the TC (ABD)begins controlling, control on and off). the control module applies negative potential to the appropriate valve coil of the valve to be con- trolled at the appropriate wheel. 4. Speed sensors The return pump relay is actuated (with a The speed sensors provide wheel speed infor- negative potential) by the control module if mation (speed information of each wheel)to the required, and closes. control module. These speed sensors operate As soon as the relay has closed / picked up, according to the inductiveprinciple, in which battery + (terminal 30) is applied to the return sinusoidalalternating voltages are generated in pump, which then runs. accordance with the number of teeth on a pulse wheel and at a frequency that is a measure of the wheel speed. 45 Function of individual components 45 -7 Printed in Germany, 1997 996451