3315751 - E7020 ABS - Functional description

Functional description

The ABS electronic control unit M50 is supplied (at pin 17 and 18) directly by the battery via a line protected by fuses F2 and F4 housed in the engine compartment junction unit B1. The supply controlled by the ignition (15/54) reaches pin 15 from the line protected by fuse F9 of junction unit B2.The control unit is earthed via pins 19 and 16. The ABS control unit M50 is connected through a CAN line from pins 29 and 30 to the engine management control unit M10 allowing the exchange of information between the two control units. The four sensors K70 , K71 , K75 , K76 send wheel speed signals to pins 6-7, 4-5, 8-9 and 1-2 of M50 respectively. The switch I30 N.A. contact is supplied when the ignition is turned on (15/54) from fuse line F1 of junction unit B2: when the brake pedal is pressed, the switch closes and sends the enablement signal to pin 14 of control unit M45. The ABS is deactivated entirely unless the brake pedal is pressed. The same signal for the brake pedal I30 is also used for operating the brake lights See E2021 BRAKE LIGHTS .

the second N.C. contact for the brake pedal I30 is only used on the VDC versionSee E7023 ESP

Pin 22 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. The red 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. The autodiagnostic data can be read by connecting to connector R10 - pin 1: it receives signals from pin 11 of the control unit M50 via the special diagnostic line See E8010 DIAGNOSTIC MULTIPLE CONNECTOR .