BRAKES - ABS
TABLE OF CONTENTS
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BRAKES - ABS
SPECIFICATIONS - TORQUE CHART ........29
ELECTRICAL
DESCRIPTION .........................29
OPERATION ...........................29
FRONT WHEEL SPEED SENSOR
REMOVAL .............................30
INSTALLATION .........................30
REAR WHEEL SPEED SENSOR
REMOVAL .............................30
INSTALLATION .........................31
TONE WHEEL
REMOVAL .............................31
INSTALLATION .........................31
HCU (HYDRAULIC CONTROL UNIT)
DESCRIPTION .........................31
REMOVAL .............................31
INSTALLATION .........................32
BRAKES - ABS
SPECIFICATIONS - TORQUE CHART
TORQUE SPECIFICATIONS
DESCRIPTION N·m Ft. Lbs. In. Lbs.
Brake Lines To Hydraulic
unit
16 — 12
ELECTRICAL
DESCRIPTION
NOTE: Wheel speed sensor should be installed all
the way into the clamping bushings, the wheel
speed sensor will self adjust when the vehicle is
moved.
The ABS brake system uses 4 wheel speed sensors.
A sensor is mounted to each front hub/bearings in
the front. A rear sensor is mounted to each rear sup-
port plate.
OPERATION
The Wheel Speed Sensor consists of a magnet sur-
rounded by windings from a single strand of wire.
The sensor sends a small AC signal to the CAB. This
signal is generated by magnetic induction. The mag-
netic induction is created when a toothed sensor ring
(exciter ring or tone wheel) passes the stationary
magnetic WSS.
When the ring gear is rotated, the exciter ring
passes the tip of the WSS. As the exciter ring tooth
approaches the tip of the WSS, the magnetic lines of
force expand, causing the magnetic field to cut across
the sensor’s windings. This, in turn causes current to
flow through the WSS circuit (Fig. 1) in one direc-
tion. When the exciter ring tooth moves away from
the sensor tip, the magnetic lines of force collapse
cutting the winding in the opposite direction. This
causes the current to flow in the opposite direction.
Every time a tooth of the exciter ring passes the tip
of the WSS, an AC signal is generated. Each AC sig-
nal (positive to negative signal or sinewave) is inter-
preted by the CAB. It then compares the frequency of
the sinewave to a time value to calculate vehicle
speed. The CAB continues to monitor the frequency
to determine a deceleration rate that would indicate
a possible wheel-locking tendency.
The signal strength of any magnetic induction sen-
sor is directly affected by:
• Magnetic field strength; the stronger the mag-
netic field, the stronger the signal
VA BRAKES - ABS 5 - 29
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