Description of operation

DESCRIPTION OF OPERATION

ABS electronic control unit M50 is supplied (at pins 17 and 18) directly by the battery via a line protected by ABS maxifuse B07.

The supply controlled by the ignition (15/54) reaches pin 15 via fuse F3 of junction unit B1.

The control unit is earthed by pins 16 and 19. 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.

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;

The ABS includes an autodiagnostics system: when the control unit detects problems relating to the ABS function it sends a signal from pin 20 to the instrument panel E50 which contains the 'ABS failure' warning light. If the problems involve the EBD function, the control unit also sends a signal from pin 21 to instrument panel E50 to the 'insufficient brake fluid level' and 'handbrake applied' warning light.

These are earth signals and make the warning lights come on because the instrument panel E50 supply is controlled by the ignition (INT) from the line protected by fuse F22 of the junction unit B1.

The self-test data can be read by connecting to connector R23: it receives signals from pin 12 of the control unit M50 via the special diagnostic line.

COMPONENTS