Honda 1996 Civic Coupe Owner's Manual page 204

Anti-lock Brake System
Only on cars equipped with ABS
The ABS works by measuring how
fast the wheels are turning during
braking and comparing their speeds.
If any wheel is rotating much slower
than the others (on the verge of
locking up and skidding), the system
reduces hydraulic pressure to that
wheel's brake. When (hat wheel's
speed matches the other wheels, the
system applies normal hydraulic
pressure. This can take place several
times per second at each wheel. You
feel the ABS working as rapid
pulsations in the brake pedal.
Technical Information
Each wheel has a wheel speed
sensor assembly. As the wheel
rotates, the sensor sends electrical
pulses to the ABS control unit. The
pulse frequency varies with the
wheel speed.
The electrical output of the ABS
control unit is connected to the
modulator/solenoid unit. While
driving, the ABS control unit
monitors the pulse frequencies from
the four wheels. When the control
unit detects a wheel locking up, it
energizes the solenoids in the
modulator unit for that wheel. The
system has eight solenoids which
work in pairs. The energized
solenoids effectively increase the
chamber volume of the brake line,
thereby reducing hydraulic pressure
to that wheel's brake. When that
wheel speeds up because of the re-
duced braking effort, the control unit
de-energizes the solenoids.
Hydraulic pressure increases in the
brake line to that wheel.
The control unit also contains error
detection circuitry. It monitors the
operation of the wheel sensors,
solenoids, pump motor, and elec-
tronics. If the control unit detects
any faults, it shuts off power to the
pump motor and solenoids, disabling
the ABS. The indicator on the instru-
ment panel comes on. The brakes
then work like a conventional system
without anti-lock capabilities.