2892663 - 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. The brake pedal switch I30 sends a go ahead signal to pin 14 of the control unit M50: in effect, the operation of the ABS is excluded unless the brake pedal is pressed; this signal arrives from the line controlled by the ignition (INT) protected by fuse F1 of the junction unit (it is the same signal which switches 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, from pin 20, 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 |