3315749 - E7020 ABS - Functional description (VDC)

Functional description

The ABS electronic control unit M50 is supplied (at pin 2 and 6) directly by the battery via a line protected by ABS maxifuse B7 . The ignition-operated supply (INT/A) reaches pin 23 from the line protected by the fuse B31 . The control unit is earthed via pins 5 and 1 ( C12 ). The four sensors K70, K71, K75, K76 send the wheel speed sensors to pins 12-28, 15-16, 13-14 and 30-31 of M50 respectively. The brake pedal switch I30 sends an enablement signal to pin 32 of control unit M50 . The ABS is deactivated entirely unless the brake pedal is pressed. Brake pedal signal I30 is also used to control the BRAKE lights ( See E2021 BRAKE LIGHTS ) and ENGINE CONTROL UNIT M10 ( See E5030 PETROL ENGINE ELECTRONIC MANAGEMENT See E5050 DIESEL ENGINES ELECTRONIC MANAGEMENT ). A second contact on brake pedal I30 (pins 3-4) sends a signal to control unit M50 at pin 20. the same signal is also sent to control unit M10, which manages the CRUISE CONTROL system  See E5060  CRUISE CONTROL . Pin 37 of M50 produces a speedometer signal (average speed of all four wheels) which is directed to instrument panel E50 - pin 2 of connector B ( See E4010 INSTRUMENT PANEL ). The ABS includes a self-diagnostic system: when the control unit detects problems with the ABS, it sends a signal from pin 20 of instrument E50 - pin 18 of connector C - which turns on the ABS fault warning light. This warning light is of the type known as 'smart' warning lights, because an inner control circuit causes the warning light to light up even if the connection is broken or if the circuit connecting warning light and control unit is short-circuited to earth. If the problems lie in the EBD function, the control unti also sends a signal from pin 21 to instrument E50 - pin 19 of connector C - to the low brake fluid and handbrake warning light. Both signals sent to the instrument are earth, and they turn on the warning lights since instrument E50 is ignition-activated (INT/A) from a line protected by fuse F1 of junction unit B1 . The self-test data can be read by connecting to connector R10 : it receives signals from pin 11 of the control unit M50 via the special diagnostic line. Wiring diagram E7020 also shows the pins of control unit M50 that manages the VDC system ( See E7022 VDC ) and the ASR/TCS system ( See E7021 ASR / TCS ).