The ABS electronic anti-lock braking system regulates the braking pressure transmitted to the wheels, preventing them from losing grip whatever the tyre and road conditions.

The system is designed to be incorporated with the braking system (using the same hydraulic fluid) without preventing the operation of the actual braking system if the ABS fails.

Four sensors, located on each of the four wheels, indicate the speed of each wheel to the electronic control unit, recording any situations involving locking, slipping or loss of grip.

In these situations, the control unit controls the solenoid valves which modulate the pressure in the hydraulic circuit, preventing the wheels from locking and restoring grip conditions for the vehicle. This ensures optimum handling of the vehicle and excellent stopping distances.

The sensors are active ones, supplied by the control unit; they consist of a magnetic resistive receiver with a magnetic codifier incorporated in the hub bearing so that the signal is less affected by electromagnetic interference and variations in temperature.

The ABS control unit also controls the distribution of the braking load between the front and rear axles, meaning that the mechanical load proportioning valve used previously can be dispensed with (EBD function: Electronic Brake Distribution ).

The control unit is equipped with a self-diagnostic function: when an error in the ABS function is detected, the warning light comes on and the system is deactivated at the same time. In these conditions the vehicle brakes using the traditional system only.

When the control unit detects an error which also affects the EBD function, it turns on the ABS failure warning light and the low brake fluid and handbrake applied warning light.

In these conditions the rear braking distribution control is deactivated: the driver must therefore proceed very carefully to the first authorised service centre.

For more details

  See descriptions 3340 ANTI-LOCK BRAKING SYSTEM (ABS) 

The ABS control unit calculates the speed of the vehicle starting from the figures that are supplied by the drive wheel sensors (with the ABS control unit calculating the average value) and from the circumference of the wheels themselves, supplied by the Body Computer: this speedometer signal is then sent, via the CAN, to the nodes that require this information. The ABS control unit also produces a discreet signal which replicates the vehicle speed information calculated and transmitted via the CAN.

The control unit supply lines are protected by dedicated fuses in the engine compartment junction unit.

The ABS electronic control unit M050 receives a power supply (at pins 1 and 25) directly from the battery from the line protected by fuses F4 and F23 of the engine compartment junction unit B001.

The ignition-controlled power supply (15/54) arrives at pin 32 from the line protected by fuse F24 of B001.

The control unit is earthed at pins 13 and 38.

The four sensors K70, K71, K75, K76 send wheel speed signals to pins 22-34, 6-18, 20-33 and 31-19 of M50 respectively.

The switch for the brake pedal I030 sends an enablement signal to control unit M050 via the CAN through the Body Computer M001: all intervention of the ABS is excluded unless the brake pedal is pressed (signal from N.A. contact); switch I030 receives an ignition-controlled power supply (INT) from fuse F37 of the Body Computer M001.

The ABS control unit M050 is connected, via the CAN line, from pins 15 and 27, to the engine management control M010 and, from pins 14 and 26, to the Body Computer M001 and to the instrument panel E050 to manage the ABS failure warning light and, if there are problems with the EBD function, the insufficient brake fluid and handbrake warning light.

The speedometer signal for all the systems that require this information is sent via the CAN.