194001717 - E7020 ABS - DESCRIPTION

The ABS electronic antilock 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, indicatae 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 which ensures optimum handling of the vehicle and excellent stopping distances.The sensors are active, i.e. they are supplied by the control unit: they consist of a magnetic-resistive receiver that faces a magnetic coding device built into the hub bearing. This ensures the signal is less sensitive to electromagnetic interference and temperature fluctuations.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 an autodiagnostic function: when an error in the ABS function is detected, the warning light comes on and, at the same time, the system is deactivated; 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" 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.
The ABS control unit also implements ESP (Elettronic Stability Program) for vehicle stability control and ASR (Anti Slip Regulation), and also HBA (Hydraulic Brake Assist) and H.H. (Hill Holder)    See E7023 ESPFor 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 actual circumference of the wheels themselves, supplied by the Body Computer: this information is then sent via the CAN to the nodes requiring this information. The ABS control unit also produces a discrete signal which replicates the vehicle speed information calculated and transmitted via the CAN.The ABS control unit software and solenoids are supplied via lines protected by special maxifuses located in the engine compartment junction unit. The INT power supply is protected by a special fuse in the under-facia junction unit.