Subaru LEGACY Installation and operation manual

MSA5AV146B

0 Copyright 1997
Subaru of America. Inc.
All rights reserved.
This book may not be reproduced in whole
or in part without the express written permission
of Subaru of America, Inc.
Subaru of America, Inc. reserves the right at any time to make changes or modifications to sys-
tems, procedures, descriptions, and illustrations contained in this book without necessarily
updating this document. Specificationsincluded are accurate as they existed at the time of pub-
lication. Information herein is considered current as of August, 1997.
0 Subaru of America, Inc. MSA5AV146B

AN INTRODUCTION TO
ABS 5.3 SYSTEM DIAGNOSIS
INTRODUCTION ............................................ 3
OVERVIEW ................................................ 4
DIFFERENCES BETWEEN THE 5.3 AND THE 5.3i .............. 6
COMPONENT LOCATIONS .................................. 7
OPERATION ................................................ 8
Pressure Decrease ............................................. 8
PressureHold ................................................ 9
Pressure Increase .............................................. 9
DIAGNOSTICS .............................................. 10
Using the New Select Monitor with the Service Manual ............... 12
Using the New Select Monitor for Diagnosis
........................ 14
15
16
BRAKEBLEEDING ......................................... 18
Sequencecontrol ............................................. 18
19
Commanding Sequence ControlWithout the Select Monitor
............
19
CONCLUSION .............................................. 19
Example of a Troubleshooting Procedure ...........................
Diagnosis Without the New Select Monitor .........................
Using the Trigger Option ....................................... 16
Checking the Pedal Stroke
......................................
2 Video Reference Booklet

AN INTRODUCTION TO
ABS 5.3 SYSTEM DIAGNOSIS
This Video Reference Booklet accompanies
the videotape “An Introduction to ABS 5.3
System Diagnosis.” It summarizes the
information contained in the videotape.
This Booklet provides an overview of the
ABS 5.3 system; it covers the differences
between the 5.3 and the 5.3i, component
locations, a brief overview of the operation
of the ABS 5.3, diagnostics, and the brake
bleeding procedure.
Before using this videotape and the
Booklet, you should meet the following
prerequisites:
1. You should be familiar with basic brake
system diagnosis and repair, including the
brake bleeding procedure.
2. You should know how ABS systems
operate.
3. You should be familiar with Subaru
Service Manuals and be able to read the
electrical wiring diagrams.
4. You should know how to operate the
New Select Monitor.
If you do not meet these prerequisites, talk
to your supervisor or district technical
manager to arrange for additional training.
Video Reference Booklet 3

AN INTRODUCTION TO
ABS 5.3 SYSTEM DIAGNOSIS
VERVIEW
The ABS 5.3 is a four-sensor, four channel
system. It controls the front wheels inde-
pendently during ABS braking. It controls
the rear wheels as a pair, as appropriate for
whichever of the two wheels is turning
more slowly.
It was introduced in 1996 on Legacy vehi-
cles equipped with ABS. More recently, an
updated system, the ABS 5.3i, has been
introduced. The 5.3i is used on the 1998
Forester, late 1997 Legacy, and late 1997
Impreza vehicles equipped with ABS.
The ABS 5.3 system has improved self-
diagnostics and trouble code memory, and
it can communicate with OBD-I1 testers,
such as the New Select Monitor.
(1) ABS control module and hydraulic (5) G sensor
(2) Proportioning valve (6) ABS warning light
control unit (ABSCM&H/U)
(9) Wheel cylinder
(1 0) Transmission control moi
AT vehicle)
(11) Brake switch
(1 2) Master cylinder
le(only
(3) Diagnosis connector (7) Tone wheel
(4) Data link connector (for SUBARU (8) ABS sensor
select monitor)
ABS 5.3i System
4 Video Reference Booklet

AN INTRODUCTION TO
ABS 5.3 SYSTEM DIAGNOSIS
NIPPON Brake lines come Under Passenger's Seat
into top
of unit. Has
brake bleeders on
top
of unit.
in top of unit in shape
of a square.
in top of unit lined up
in straight line.
BOSCH Brake lines come Under Passenger's Seat
ABS-2E Brake lines come Under Passenger's Seat
19961Early 1997Legacy 1998 Forester
No No
No No
Yes No
90-94 Legacy
Hydraulic Unit Computer Location Long Term Memory?
ABS-2E Brake lines come in Under Passenger's Seat Yes
top
of unit lined in
straight line.
come in top and two
in side
of unit.
brake lines come in
the side
of the unit.
brake lines come in
the top in the shape
of a square.
ABSiTCS
95 Two brake lines Under Passenger's Seat Yes
front wheel drive
Legacy Auto only
ABS 5.3 Motor stands upright, To the right
of the glove box in the Yes
Legacy. To the left
of the steering
colum in the Impreza.
ABS 5.3i Motor lies down, Computer part
of the Hydraulic unit. Yes
-.
Hydraulic Unit I Computer Location I Long Term Memory? I Select Monitor? I
Select Monitor?
No
Yes
Yes
Yes
1993-97lmpreza - ABS-2E
1997 lmpreza
- ABS 5.3
1998 lmpreza
- ABS 5.3i
1992-96
SVX - Nippon
1998 Forester
- ABS 5.3i
ABS Applications
Video Reference Booklet 5

AN INTRODUCTION TO
ABS 5.3 SYSTEM DIAGNOSIS
8 Dahlink connector (for SUBARU
(2, Transmission controlmodule
@I ABS sensor
@ Hydraulic control unit
@ Proportimingvaive select monitor) @ Whedcylinder
03 0 sensor (only AWD vehicle)
0 ABS control module
@ Diagnosisconnector (only AT vehicle) @ Brakeswitch
@ ABS warning laht @ Tonewheei 0 Mastercylinder
03 fleiay box
i
ABS 5.3 System
Although the ABS 5.3 and 5.3i systems are
similar
in most ways, there are a fen!
important differences.
On the ABS 5.3, the ABS control unit is
located behind and to the right
of the glove
box. With the 5.3i, the ABS control
unit is
mounted on the Hydraulic Control Unit
(HCU).
The Select Monitor can communicate only
with the
ABS 5.3. The New Select
Monitor can communicate with both the
5.3 and 5.3i, using the appropriate car-
tridges.
Select Monitor (Left) and
New Select Monitor (Right)
6 Video Reference Booklet

AN INTRODUCTION TO
ABS 5.3 SYSTEM DIAGNOSIS
OMPONENT LOCATIONS
Most of the ABS 5.3 and 5.3i components
are located in the engine compartment.
The HCU is located under the hood at the
front right corner. It contains the solenoid
valves used to control hydraulic pressure to
the wheels during ABS braking, as well as
the motor pump assembly and the relays.
In the 5.3i version, the ABS control unit is
mounted on the HCU, instead
of behind the
glove box.
For both models, the
G sensor is located
under the center console.
It senses acceler-
ation and deceleration,
so that the ABS
control unit can compare the actual speed
of the vehicle with the speed reported by
the wheel speed sensors.
DIAGNOSIS CONNECTOR
DiagnosisConnector
The diagnosis connector is located above
the accelerator pedal. It can be used to
manually read and clear trouble codes.
ConnectingCable to Data Link Connector
The Data Link Connector (DLC) is located
under the dash panel on the driver’s side.
It
allows the New Select Monitor to commu-
nicate with several of the vehicle’s systems,
including the ABS.
At each wheel, there’s a speed sensor and a
tone wheel. The tone wheel provides a
magnetic pulse to the wheel speed sensor,
which the ABS control unit uses to deter-
mine the speed
of rotation of the wheel.
I
Wheel Speed Sensor and Tone Wheel
Video Reference Booklet 7

AN INTRODUCTION TO
ABS 5.3 SYSTEM DIAGNOSIS
PERATION
Hydraulic fluid is directed from the master
cylinder to the brake calipers at each
wheel, where the
HCU controls brake fluid
flow by means of eight solenoid valves.
There
is an inlet valve and an outlet valve
for each wheel. During normal braking,
the inlet valve is open and the outlet valve
is closed.
There are three ABS modes: Pressure
Decrease, Pressure Hold, and Pressure
Increase. When the ABS control unit sens-
es that one
or more of the wheels is starting
to lock up, it activates the ABS system and
controls braking for the affected wheel, in
these ABS modes.
It also activates the
motor-pump assembly.
Pressure Decrease
In the Pressure Decrease mode, the HCU
closes the inlet solenoid valve, shutting off
pressure from the master cylinder to the
brake caliper at the affected wheel. At the
same time it opens the outlet solenoid
valve, releasing brake fluid pressure from
the caliper, reducing braking at that wheel.
DAMPER
FROM MASTER CYLINDER CHAMBER
RESERVOIR
HydraulicSystem - NormalBraking
DAMPER
FROM MASTER CYLINDER CHAMBER
II n
INTLET kl
I33
RESERVOIR
HydraulicSystem - PressureDecrease
8 Video Reference Booklet