when the tires ride on a film of water, resulting in the
tire leaving the road surface rendering the vehicle
almost uncontrollable. In addition, extreme steering
maneuvers at high speed or high speed cornering
beyond the limits of tire adhesion to the road surface
may cause vehicle skidding, independent of vehicle
braking. So, the ABS system is termed Anti-Lock
instead of Anti-Skid.
One of the significant benefits of the ABS system is
that of maintaining steering control during hard brak-
ing or during braking on slippery surfaces. It is there-
fore possible to steer the vehicle while braking on
almost any road surface.
ABS SYSTEM SELF-DIAGNOSTICS
The ABS system has been designed with Self Diag-
nostic Capability. There are two self checks the sys-
tems performs every time the vehicle is started. First,
when the key is turned on the system performs an
electrical check called Start-Up Cycle. During this
check, the Red Brake Warning Lamp and the Amber
Anti-Lock Warning Lamp are illuminated. Then
turned off at the end of the test, after about 1 to 2
seconds. When the vehicle reaches a speed of about 3 to
4 miles per hour. The system performs a functional
check called Drive-Off. During Drive-Off. hydraulic
valves are activated briefly to test their function.
Drive-Off can be detected as a series of rapid clicks
upon driving off the first time the car is started. If the
brake pedal is applied during Drive-Off, the test is
by-passed. Both of these conditions are a normal part
of the system self test. Most fault conditions will set a
ABS Fault Code in the (CAB), which can be retrieved to
aid in fault diagnosis. Details can be found in Diagno-
sis Section.
WARNING SYSTEMS OPERATION
The ABS system uses two methods for notifying the
driver of a system malfunction. These include the
standard Red Brake Warning Lamp and an Amber
Anti-Lock Warning Lamp, both located in the instru-
ment cluster. The purpose of these two lamps are
discussed in detail below.
RED BRAKE WARNING LAMP
The Red Brake Warning Lamp, located in the instru-
ment cluster, will Turn On to warn the driver of brake
system conditions that may result in reduced braking
ability. The lamp is also turned on when the parking
brake is not fully released. Conditions which may
cause the Red Brake Warning Lamp to Turn On
include:
• Parking brake not fully released. If the parking
brake is applied or not fully released. The switch on the
parking brake pedal assembly will ground the Red
Brake Warning Lamp circuit and cause the lamp to
turn on. On vehicles equipped with mechanical instru-
ment clusters, the Amber Anti-Lock Lamp will turn on
if the vehicle is driven above 3 miles per hour with the
Parking Brake applied.
• Low brake fluid. The fluid level sensor in the hy-
draulic assembly reservoir will ground the Red Brake
Warning Lamp circuit if low brake fluid level is de-
tected. In addition, ABS will be deactivated above 3
miles per hour and the Amber Anti-Lock Warning
Lamp will be illuminated. If the vehicle is equipped
with EVIC, a low fluid condition will also cause the
Low Brake Fluid message to appear.
• Low accumulator pressure. In the event of low
accumulator pressure, the dual function pressure
switch in the hydraulic assembly will signal the (CAB)
to ground the Red Brake Warning Lamp circuit. This
will cause the Red Brake Warning Lamp to turn on.
Low accumulator pressure may result in loss of power
assist.
• Hydraulic assembly or (CAB) faults. The hydraulic
assembly or (CAB) may turn on the Red Brake Warn-
ing Lamp. If certain faults are detected in either the
hydraulic assembly or the (CAB), or the normal brake
system.
• Bulb check. As a bulb check, the Red Brake Warning
Lamp will illuminate whenever the ignition switch is
placed in the crank position.
• Illumination of the red Brake Warning Lamp
may indicate reduced braking ability. A vehicle
that has the Red Brake Warning Lamp ON should
not be driven except to do diagnostic procedures
described in Section 2 of this manual. Most con-
ditions that turn on the Red Brake Warning
Lamp will also turn on the Amber Anti-Lock
Warning Lamp, consequently disabling the Anti-
Lock function.
ANTI-LOCK WARNING LAMP
The Anti-Lock Warning Lamp is located in the in-
strument cluster and is Amber in color. The Amber
Anti-Lock Warning Lamp is illuminated when the
(CAB) detects a condition that results in a shutdown of
Anti-Lock function. The Amber Anti-Lock Warning
Lamp is normally on until the (CAB) completes its self
tests and turns the lamp off. For example, if the (CAB)
is disconnected, the lamp is on.
Display of the Amber Anti-Lock Warning Lamp
without the Red Brake Warning Lamp indicates
only that Anti-Lock function has been disabled.
Power assisted normal braking is unaffected.
NORMAL OPERATION OF WARNING LAMPS
With the ignition in the Crank position, the Red
Brake Warning Lamp will turn on as a bulb check. The
Amber Anti-Lock Warning Lamp will turn on for as
little as 1 second to as long as 30 seconds.
If the car has not been started for several hours, for
example after sitting overnight. The Red Brake Warn-
ing
Lamp
and
the
Amber
Anti-Lock
Warning
.
ANTI-LOCK BRAKES
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