1994 Honda Civic Owner's Manual - Page 184

1994 Honda Civic Manual

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Anti-Lock Brake System On U.S. EX with ABS option The ABS works by measuring how fast the wheels are turning during braking and comparing their speed. 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 caliper. When that 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. 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. During braking, the ABS control unit monitors the pulse frequencies from the four wheels. When the control unit detects a wheel locking up, it energizes the appropriate solenoid in the modulator/solenoid unit. There are three solenoids: one for each front wheel, and one for the rear wheels. The energized solenoid reduces hydraulic pressure to one side of a modulator valve. This, in turn, reduces hydraulic pressure in the brake line going to the affected wheel. When that wheel speeds up because of the reduced braking effort, the control unit de-energizes the solenoid. This builds hydraulic pressure on the modulator valve. The pressure increases in the hydraulic line to the wheel. For the system to react quickly, the modulator/solenoid unit must have brake fluid under high pressure. This is supplied by a diaphragm-type accumulator that is pressurized by an electric pump. A pressure-sensing switch on the accumulator controls this pump. The control unit also contains error detection circuitry. It monitors the operation of the wheel sensors, solenoids, pump, and electronics. If the control unit detects any faults, it shuts off power to the pump motor and solenoids. The light on the instrument panel comes on. The brakes then work like a conventional system without anti-lock capabilities. Technical Information

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Anti-Lock Brake System
On U.S. EX with ABS option
The ABS works by measuring how
fast the wheels are turning during
braking and comparing their
speed. If any wheel is rotating
much slower than the others (on
the verge of locking up and
skidding), thesystemreduces
hydraulic pressure to that wheel's
brake caliper. When that 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 theABS
working as rapid pulsations in the
brake pedal.
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. During
braking, the ABS control unit
monitors the pulse frequencies
from the four wheels. When the
control unit detects a wheel
locking up, it energizes the
appropriate solenoid in the
modulator/solenoid unit. There
are three solenoids: one for each
front wheel, and one for the rear
wheels. The energized solenoid
reduces hydraulic pressure to one
side of a modulator valve. This, in
turn, reduces hydraulic pressure
in the brake line going to the
affected wheel. When that wheel
speeds up because of the reduced
braking effort, the control unit
de-energizes the solenoid. This
builds hydraulic pressure on the
modulator valve. The pressure
increases in the hydraulic line to
the wheel.
For the system to react quickly,
the modulator/solenoid unit must
have brake fluid under high
pressure. This is supplied by a
diaphragm-type accumulator that
is pressurized by an electric
pump. A pressure-sensing switch
on the accumulator controls this
pump.
The control unit also contains
error detection circuitry. It
monitors the operation of the
wheel sensors, solenoids, pump,
and electronics. If the control unit
detects any faults, it shuts off
power to the pump motor and
solenoids. The light on the
instrument panel comes on. The
brakes then work like a
conventional system without
anti-lock capabilities.
Technical Information