Dodge RAM TRUCK 1500 1995 Service Manual page 210

S - 38 ILL-WHEEL ANTILOCK BRAKE SYSTEM (ABS) B i t
SENSOR
BOLTS (2)
STEERING
KNUCKLE
SPLASH
SHIELD
FRONT
SENSOR J9505-118
Fig. 4 Front Wheel Sensor Location
-ROTOR
J9305-71
Fig. 5 Front Tone Wheel Location (In Rotor)
same master cylinder and dual or single diaphragm
boosters are used with either antilock system.
ALL WHEEL ANTILOCK SYSTEM (ABS) OPERATION
The all wheel ABS system is a three channel de­
sign. The front wheel brakes are controlled individu­
ally and the rear wheel brakes in tandem (Fig. 7).
The ABS system is designed to retard wheel lockup
during periods of high wheel slip when braking. Re­
tarding wheel lockup is accomplished by modulating
fluid pressure to the wheel brake units.
The antilock electrical system is separate from
other electrical circuits in the vehicle. A specially pro­
grammed electronic control module is used to operate
the system components.
The front and rear antilock valves contain electri­
cally operated solenoid valves. The solenoid valves
modulate brake fluid apply pressure during antilock
braking. The valves are operated by the antilock elec­
tronic module.
RFTAINING _
SCREW
CABLE ~~~~~~~~~~
CLAMP——""^
BRAKE
LINE
C O V E R - ^ * " ^
SENSOR' ~~~~~
A X L E _ „ —
HOUSING
Fig. 6 Rear Wheel Sensor Location
The ABS valve provides two channel pressure con­
trol of the front brakes. Each front wheel brake unit
is controlled separately. Two solenoid valves are used
in each control channel.
The RWAL valve controls the rear wheel brakes in
tandem. The rear brake valve contains two solenoid
valves.
During antilock braking, the solenoid valves are
opened and closed as needed. The valves are not
static. They are cycled rapidly and continuously to
modulate pressure and control wheel slip and decel­
eration.
The pump/motor assembly on the front antilock
valve provides the fluid volume needed during an­
tilock braking. The pump is operated by an integral
electric motor. The DC type motor is controlled by
the ABS control module.
mS O P E R A T I O N IN NORMAL BRAKING MODE
The ABS electronic control module monitors wheel
speed sensor inputs continuously while the vehicle is
in motion. However, the module will not activate any
ABS components as long as sensor inputs indicate
normal braking.
During normal braking, the master cylinder, power
booster and wheel brake units all function as they
would in a vehicle without ABS. The solenoid valves
are not activated.