Chrysler 1997 Stratus Convertible RHD Service Manual page 172

5 - 70 BRAKES
DESCRIPTION AND OPERATION (Continued)
ABS BRAKING MODE HYDRAULIC CIRCUIT
SOLENOID AND VALVE FUNCTION
Through the following operation descriptions the
function of the various hydraulic control valves in the
ABS system will be described. The fluid control
valves mentioned below, control the flow of pressur-
ized brake fluid to the wheel brakes during the dif-
ferent modes of ABS braking.
For explanation purposes we will assume all speed
sensors are sending the same wheel speed informa-
tion, requiring the same hydraulic fluid modulation
at the same rate.
NORMAL BRAKING BUILD/DECAY VALVE
FUNCTION
BUILD/DECAY VALVES OPEN
The brake pedal is applied. The travel of the brake
pedal closes primary and secondary circuits from the
master cylinder fluid supply. Brake fluid from the
primary and secondary circuits flows through the
build/decay valves to the wheel brakes.
ABS BRAKING-DECAY MODE-DECAY
SOLENOID FUNCTION
DECAY SOLENOID ENERGIZED
This will allow brake hydraulic pressure to be
dumped to the HCU sump. At the HCU sump, the
brake hydraulic fluid is picked up by the pump and
restored to high pressure for the next build cycle.
ABS BRAKING-BUILD MODE-DECAY
SOLENOID FUNCTION
DECAY SOLENOID DE-ENERGIZED
Decayed brake fluid, is picked up by the pump in
the HCU and restored to high pressure. This high
pressure brake fluid causes the shuttle valve in the
HCU to actuate, routing high pressure brake fluid
through the build orifice. Routing the high pressure
brake fluid through the build orifice allows for a con-
trolled build pressure in the brakes hydraulic system.
High pressure brake fluid from the build orifice then
passes through the de-energized decay solenoid and
to the wheel brakes to restore braking pressure.
DIAGNOSIS AND TESTING
ABS GENERAL DIAGNOSTICS INFORMATION
This section contains information necessary to
diagnose and test the Allied Signal ABX-4 Brake Sys-
tem. Specifically, this section should be used to help
diagnose conditions which result in any of the follow-
ing conditions:
• ABS Warning Lamp turned on.
• Brakes Lock on Hard Application
Diagnosis of base brake conditions which are obvi-
ously mechanical in nature should be directed to
Group 5 Brakes in this service manual. This includes
brake noise, brake pulsation, lack of power assist,
parking brake, Red Brake Warning Lamp lighting, or
vehicle vibration during normal braking.
Many conditions that generate customer com-
plaints may be normal operating conditions, but are
judged to be a problem due to not being familiar with
the ABS system. These conditions can be recognized
without performing extensive diagnostic work, given
adequate understanding of the operating principles
and performance characteristics of the ABS system.
See the ABS System Operation section in this group
of the service manual to familiarize yourself with the
operating principles of the ABS system.
DIAGNOSTICS MANUAL INFORMATION
Detailed procedures for diagnosing specific ABS
conditions are covered in the Allied Signal ABX-4
diagnostics manual. The following information is pre-
sented to give the technician a general background
on the diagnostic capabilities of the ABX-4 ABS sys-
tem. Please refer to the above mentioned manual for
any further electronic diagnostics and service proce-
dures that are required on the Allied Signal ABX-4
Brake System.
DIAGNOSTIC TESTER (DRB)
The Allied Signal ABX-4 Antilock Brake System
diagnostics are performed using the DRB scan tool.
Refer to the Allied Signal ABX-4 diagnostic manual
for the proper testing procedures and the DRB oper-
ators manual for its proper operational information
when diagnosing this brake system.
ABS (DRB) DIAGNOSTIC CONNECTOR
On this vehicle, the ABX-4 diagnostic connector is
located under the lower instrument panel directly
next to the left kick panel (Fig. 7). The ABX-4 system
uses the ISO 9141-K connector which is shared by
other vehicle diagnostic systems such as the power-
train control module and air bag.
SELF DIAGNOSTICS INFORMATION
The ABX-4 system is equipped with a self diagnos-
tic capability which may be used to assist in isolation
of ABS faults. The features of the self diagnostics
system are described below.
START-UP CYCLE
The self diagnostic ABS start up cycle begins when
the ignition switch is turned to the on position. Elec-
trical checks are completed on ABS components, such
as the Controller, decay solenoid continuity, and the
system relay operation. During this check the Amber
ABS Warning Light is turned on for approximately 5
seconds.
JX