Chrysler Concorde 1993 Service Manual page 172

5 - 78 ANTI-LOCK BRAKE SYSTEM
Fig. 5 Wheel Speed Sensor
ered normal. These characteristics are discussed be-
low. More technical details are discussed further in
this section.
PEDAL FEEL
Since the Teves Mark IV Anti-Lock braking system
uses the conventional booster/master Cylinder. The
brake pedal feel during normal braking is the same
as conventional Non ABS equipped cars.
When Anti-Lock is activated during hard braking
due to a wheel lockup tendency. Brake pedal effort
will increase do to the master cylinder pressure be-
ing isolated from the brake system. Some brake
pedal movement and associated noises may be felt
and heard by the driver. This is normal of a Anti-
Lock Braking System due to pressurized fluid being
transferred to and from the wheel brakes.
ANTI-LOCK BRAKE SYSTEM OPERATION
During Anti-Lock Braking, brake pressures are
modulated by cycling electric solenoid valves. The cy-
cling of these valves can be faintly heard as a series
of popping or ticking noises. In addition, the cycling
may be felt as a pulsation in the brake pedal. If An-
ti-Lock Operation occurs during hard braking, some
pulsation may be felt in the vehicle body due to fore
and aft movement of the suspension as brake pres-
sures are modulated.
Although ABS operation is available at virtually
all vehicle speeds. It will automatically turn off at
speeds below 3 to 5 mph. Wheel lockup may be per-
ceived at the very end of an anti lock stop and is con-
sidered normal.
TIRE NOISE & MARKS
Although the ABS system prevents complete wheel
lock-up, some wheel slip is desired in order to
achieve optimum braking performance. During brake
pressure modulation, as brake pressure is increased,
wheel slip is allowed to reach up to 30%. This means
that the wheel rolling velocity is 30% less than that
of a free rolling wheel at a given vehicle speed. This
slip may result in some tire chirping, depending on
the road surface. This sound should not be inter-
preted as total wheel lock-up.
Complete wheel lock up normally leaves black tire
marks on dry pavement. The Anti-Lock Braking Sys-
tem will not leave dark black tire marks since the
wheel never reaches a locked condition. Tire marks
may however be noticeable as light patched marks.
VEHICLE PERFORMANCE
Anti-Lock Brakes provide the driver with some
steering control during hard braking, however there
are conditions where the system does not provide any
benefit. In particular, hydroplaning is still possible
when the tires ride on a film of water. This will re-
sult in the tire leaving the road surface rendering
the vehicle virtually uncontrollable. In addition, ex-
treme steering maneuvers at high speed or high
speed cornering beyond the limits of tire adhesion to
the road surface may cause vehicle skidding, inde-
pendent of vehicle braking. For this reason, the ABS
system is termed Anti-Lock instead of Anti-Skid.
SYSTEM DIAGNOSTIC FEATURES
The Teves Mark IV Anti-Lock brake system has
been designed with the following self diagnostics ca-
pability.
The (CAB) uses two microprocessors housed in the
controller to monitor and control the Anti-Lock and
Traction Control systems. The microprocessors oper-
ate independently, and compare their results.
Fault messages are retained in a non-volatile mem-
ory until erased using the DRBII scan tool or auto-
matically erased after 50 ignition key cycles. More
than one fault can be stored in the memory at a
time. The number of faults stored is displayed by the
DRBII scan tool when Read Faults is selected.
SYSTEM INITIALIZATION
System initialization starts when the ignition
switch is turned to the run position. At this point the
(CAB) performs a complete self check of all electrical
components in the Anti-Lock and Traction Control
systems. Momentarily the build, decay and isolation
valves are cycled. If the driver has his their foot on
the brake pedal, they may feel the test through
brake pedal pulsations. This is a normal condition.
DYNAMIC TEST
Between 5 - 10 mph the pump/motor is momen-
tarily turned on.
If any component exhibits a fault during system
initialization or dynamic check, the (CAB) will illu-
minate the Anti-Lock warning lamp and Traction
Control Function Lamp. At this time both systems
are disabled.