184002348 - E7020 ABS - DESCRIPTION

Description

The electronic anti-lock brake system ( BOSCH 8.0 ABS) governs braking pressure sent to the wheels and prevents loss of grip under all tyre and road surface conditions.The system is designed to be integrated with the braking system (using the same hydraulic fluid) without preventing the operation of the braking system if the operation of the ABS fails.Four sensors fitted to the four wheels inform the electronic control unit of wheel speed at every moment. In this way, they detect wheel lock, wheel slip and loss of grip.Under these conditions, the control unit sends specific instructions to solenoids that modulate hydraulic circuit pressure to eliminate lock and restore the car to within grip limits which allows optimum driveability and stopping distances.The sensors are the ''active'' type, i.e. supplied by the control unit; they consist of a receiver that faces a magnetic coding device built into the hub bearing so that the signal is less influenced by electromagnetic interference and variations in temperature.The ABS control unit also controls brake force distribution of the rear axle in relation to the front axle, allowing the mechanical load proportioning device used previously to be dispensed with (EBD function: Electronic Brake Distribution).The control unit is equipped with a self-diagnostic function: when an error is detected in the ABS function the warning light comes on and the system is simultaneously deactivated; Under these conditions, the car brakes using only the conventional system.When the control unit detects an error which also affects the operation of the EBD logic, the ''ABS failure'' warning light and the ''insufficient brake fluid level'' and ''handbrake applied'' warning light comes on.

Under these conditions, the rear brake distribution control is also deactivated: the customer must therefore drive very carefully to the first service centre.

The general failure warning light comes on if the instrument panel detects an ABS failure warning light fault.

For more details    See descriptions 3340 ANTI-LOCK BRAKING SYSTEM (ABS).The ABS control unit computes vehicle speed on the basis of values supplied by drive wheel sensors (the ABS control unit computes an average reading) and true wheel circumference supplied by the body computer. This speed signal is then sent to nodes that require the information via the CAN network. The ABS control unit also generates a discrete signal that copies the vehicle speed information computed and transmitted via the CAN network.The control unit supply lines are protected by a special maxifuse located in the engine bay control unit. ignition-operated power supply from a special fuse in the underfacia control unit.