Dodge RAM TRUCK 1500 1995 Service Manual page 208

5 - 36 ALL-WHEEL ANIiLOCI BFtAlE SYSTEM (ABS)
B R
A L L - W H E E L
A H Y I L O C 1 C B R A K E
SYSTEM {ABS}
iiDEX
page
ABS Components 36
A B S Control Module Diagnosis 40
A B S Diagnostic Connector Location . . . . . . . . . . . 40
A B S Manual Brake Bleeding Procedure . . 46
A B S Normal and Fault Conditions 40
A B S System Brake Bleeding 44
A B S System Diagnosis 39
A B S Valve and Control Module Installation . . . . . . . 41
A B S Valve and Control Module Removal . . . . . . . . 41
A B S Valve Service and Diagnosis . . . . . . . . . . . . . 41
A B S Warning Light Display 40
ABS COMPONENTS
The all-wheel antilock brake system (ABS), is a
unique combined system. It consists of the standard
rear wheel antilock (RWAL) system components, plus
the additional parts needed to create an all wheel an­
tilock brake system.
ABS components include:
© rear brake (RWAL) antilock valve
® rear wheel speed sensor and exciter ring
• front wheel speed sensors and tone rings
• front brake antilock valve
© ABS electronic control module
o electrical harnesses
o combination valve
© diagnostic connector
Front Brake ABS Valve
The front brake ABS valve consists of a solenoid
valve body and pump/motor unit combined into a sin­
gle assembly (Fig. 1).
The valve is mounted on the driver side inner
fender panel (Fig. 1). The valve and motor assembly
are attached to a one piece mounting bracket and a
stud plate. A molded, flexible shield is used to protect
the top of the valve * assembly.
The valve body contains the solenoid valves that
modulate brake fluid apply pressure during antilock
braking. The valves are operated by the antilock sys­
tem electronic control module.
The antilock valve provides two channel pressure
control of the front brakes. One channel controls the
left front brake unit. The second channel controls the
right front brake unit. Each front brake unit is con­
trolled independently.
The solenoid valves are cycled open and closed as
needed during antilock braking. The valves are not
static. They are cycled rapidly and continuously to
modulate pressure and control wheel slip and decel­
eration.
The pump and motor are controlled by the elec-
page
All Wheel Antilock System (ABS) Operation 38
Combination Valve Operation 39
Combination Valve Testing 41
Front Speed Sensor Installation 43
Front Speed Sensor Removal 43
Front Tone Wheel Service . . . . . . . . . . . . . . . . . . . 44
Rear Speed Sensor Harness Replacement . . . . . . 44
Rear Speed Sensor Installation . 44
Rear Speed Sensor Removal/Installation . . . . . . . . 44
RWAL Valve/Combination Installation . . . . . . . . . . . 43
RWAL Valve/Combination Valve Removal . . . . . . . 42
tronic control module. The pump supplies the addi­
tional fluid volume needed during antilock braking.
Fig. 1 ABS Component Location
RWAL
V a l v e
The RWAL valve is mounted on the combination
valve bracket (Fig. 2). The bracket is secured to the
master cylinder mounting studs on the power brake
booster.
The RWAL valve modulates rear brake apply pres­
sure during antilock braking. The valve is controlled
and operated by the electronic control module. Two
solenoid valves in the RWAL valve isolate, decrease,
or increase rear brake pressure as needed during an­
tilock braking.
The solenoid valves are inactive during periods of
normal braking. The solenoids allow free flow of
brake fluid to the wheel cylinders during normal