2892665 - E7020 ABS - Functional description

Functional description

ABS electronic control unit M50 is supplied (at pin 17 and 18) directly by the battery via a line protected by ABS maxifuse B7 . The supply controlled by the ignition (15/54) reaches pin 15 from the line protected by the specific fuse B31 . The control unit is earthed via pins 19 and 16. The four sensors K70 , K71 , K75 , K76 send wheel speed signals to pins 6-7, 4-5, 8-9 and 1-2, respectively of M50 . Brake pedal switch I30 sends an enablement signal to pin 14 of control unit M50 : the ABS cannot intervene unless the brake pedal is pressed; this signal arrives from the ignition-operated line (INT) protected by the fuse F1 of the junction unit (it is the same signal which turns on the lights -  See E2021  BRAKE LIGHTS ). If the control unit M50 detects problems relating to the ABS function, it sends the instrument panel E50 a signal, pin 4 of connector A, which lights up the 'ABS failure' warning light.

the 'ABS failure' warning light is a so-called 'intelligent' light: thanks to a special operating circuit inside the instrument, it not only comes on to signal a fault in the ABS system, but also if there is no connection or a short circuit to earth in the circuit which connects the instrument with the control unit

If the problems involve the EBD function, the control unit also sends a signal from pin 21 to the 'insufficient brake fluid level and handbrake' warning light which comes on together with the 'ABS failure' warning light. pin 14 of connector C of E50 . This is an earth signal and makes the warning light come on because the instrument panel E50 supply at pin 19 of connector A is controlled by the ignition (INT) from the line protected by fuse F1 of the junction unit B1 . The autodiagnostic 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.