10-54891-01
Warning Lamps
EBD warning lamp ABS warning lamp
2. COMPONENTS AND LAYOUT
The basic functions of ABS system are same with previous version. However, the wheel speed sensing
type is different from previous version.
For details about the components, refer to Chapter "ESP".
Front Active Wheel Speed Sensor
4WD 2WD
ABS HECU
Rear Active Wheel
Speed Sensor
10-74891-01
2) EBD (Electronic Brake Force Distribution) System
▶System description
As an add-on logic to the ABS base algorithm, EBD works in a range in which the intervention
thresholds for ABS control are not reached yet.
EBD ensures that the rear wheels are sensitively monitored for slip with respect to the front axle. If slip is
detected, the inlet valves for the rear wheels are switched to pressure hold to prevent a further increase
in pressure at the rear-wheel breaks, thus electronically reproducing
a pressure-reduction function at the rear-wheel brakes.
ABS features an enhanced algorithm which includes control of the brake force distribution between the
front and rear axles. This is called Electronic Brake Distribution. In an unloading car condition the brake
efficiency is comparable to the conventional system but for a fully loaded vehicle the efficiency of the
EBD system is higher due to the better use of rear axle braking capability.
▶Advantages
Elimination of conventional proportioning valve EBD utilizes the existing rear axle wheel speed
sensor to monitor rear wheel slip.
Based on many variables in algorithm a pressure hold, increase and/or decrease pulsetrain may be
triggered at the rear wheels insuring vehicle stability.
Vehicle approaches the ideal brake force distribution (front to rear).
Constant brake force distribution during vehicle lifetime.
EBD function is monitored via ABS safety logic (conventional proportioning valves are not
monitorable). ·
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3) Important Notice
The modulators for production line are not filled with the brake fluid (dry type). But, for after service, they
are filled with the brake fluid (wet type).
Make sure to keep the procedures in service manual when bleeding the air from the brake lines.
Be familiar with the lamp ON conditions to provide the correct information and reliability to customers.
ECU monitors the valve and motor for ABS when the vehicle speed approaches 5 km/h. At this time, you
can hear the clattering noise. 1.
2.
3.
12-8
If weight is not equally distributed around the wheel, unbalance centrifugal force by the wheel
rotation produces vibration. As the centrifugal force is produced proportional to the square of the
rotating speed, the wheel weight should be balanced even at high speed. There are two types of
the tire and wheel balancing: static and dynamic. Abnormal vibration may also occur due to
unbalanced rigidity or size of tires.
1) Static Balance
When the free rotation of the wheel is
allowed, the heavier part is stopped on the
bottom if the wheel weight is unbalanced
and this is called "Static Unbalance". Also,
the state at which tire's stop position is not
same is called "Static Balance" when the
wheel is rotated again. If the part A is
heavier as shown in the figure 1, add the
balance weight of a weight corresponding
to unbalanced weight from B to A to
maintain the static balance. If the static
balance is not maintained, tramping, up
and down vibration of the wheels, occurs.
2) Dynamic Balance
The static unbalance of the wheel
creates the vibration in the vertical
direction, but the dynamic unbalance
creates the vibration in the lateral
direction. As shown in the figure 2 (a), if
two parts, (2) and (3), are heavier when
the wheels are under the static balance
condition, dynamic unbalance is
created, resulting in shimmy, left and
right vibration of the wheels, and the
torque Fxa is applied in the axial
direction. To correct the dynamic
unbalance, add the balance weight of a
same weight for two points of the
circumference of the rim, A and B, as
shown in the figure 2 (b), and apply the
torque in the opposite direction to the
torque Fxa to offset in order to ensure
smooth rotation of the wheel.
Center
A
B
a
a
Fxa
Fxa F
F
A
B
(a)(b)
[Figure 1]
[Figure 2]
3. WHEEL BALANCE
