The electronic anti-lock brake system (BOSCH
5.3 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 complement, not
replace the normal mechanical braking system and thus ensure effective
safety in the case of faults. The system works using the conventional
mechanical brake fluid circuit.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. This ensures the shortest possible stopping distance,
without losing control of the steering. Two adjustment solenoids (one for pressure
charging, the other for pressure discharging) are fitted for each
wheel.The sensors are active, i.e. they consist
of a Hall-effect receiver that faces a magnetic coding device built
into the hub bearing. Under these conditions, the signal is less
influenced by electromagnetic interference and temperature. The control unit also controls brakeforce
distribution over the rear axle and thus replaces the mechanical
lload proportioning valve used previously (EBD function: Electronic Brake
Distribution).The control unit comes 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 in
the EBD function, it simultaneously turns on the 'insufficient brake
fluid level' and 'handbrake on' warning light as well as the ABS warning
light.Under these conditions, the rear brake distribition
control is also deactivated; the car must therefore be driven be
great caution.
For more details
Characteristic of working principle 3340 A(B.S. ANTI-LOCK BRAKING
SYSTEM .)
.
Supply lines to the control unit and the
various system components (sensors and actuators) are protected
by a maxifuse and a jumper fuse located in the engine bay.