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

‘ AN INTRODUCTION TO
ABS 5.3 SYSTEM DIAGNOSIS
The ABS 5.3 system has extensive self-
diagnostic capabilities. When the ignition
switch is turned from “Off” to “On,” the
ABS system performs an electrical self-
check and illuminates the ABS warning
light for
1 1/2 seconds. If there are no
electrical problems, the system then turns
the light
off.
ABS Warning Light
The ABS 5.3 system performs a second
check when vehicle speed reaches 3 mph
(if the brake has not been applied) or
8
mph (if the brake has been applied).
During this second self-check, the ABS
system operates its motor pump for
0.2 sec-
ond and exercises the solenoids.
If the ABS control unit does not detect any
problems it keeps the ABS warning light
off. If the control unit does find a prob-
lem, it turns the ABS warning light on and
stores one or more trouble codes. The ABS
system then remains passive even if a
wheel begins to lock up.
If the problem involves one of the wheel
speed sensors, with the ABS 5.3i, the sys-
tem waits until the next ignition cycle
before turning the ABS warning light on.
If, at the next ignition cycle, the ABS sys-
tem sees the same wheel speed sensor
problem again, it turns on the ABS warning
light and the system stays passive,
Otherwise, the ABS system assumes there
is no problem.
New Select Monitor - “Each System
Check” Selected
If a vehicle with an ABS 5.3 or 5.3i system
has an ABS warning light that stays on,
you can use the New Select Monitor to
read its trouble codes. Simply plug in the
New Select Monitor, turn the ignition
switch to “On,” and select “Each System
Check” from the main menu.
New Select Monitor - “ABSRCS” Selected
Next, select “ABS/TCS.”
10 Video Reference Booklet

AN INTRODUCTION TO
ABS 5.3 SYSTEM DIAGNOSIS
10AJ1 : CHECK ALL FOUR WHEELS FOR
FREE TURNING.
New Select Monitor - “ABSAWD AT?”
10AJ2 : CHECK OUTPUT OF 0 SENSOR
USINGSELECT MONITOR.
The New Select Monitor now asks you
whether the vehicle has all-wheel drive and
automatic transmission. Press the “Yes”
button, then select “Diagnostic Code(s)
Display.” The New Select Monitor will
display the trouble codes stored in the ABS
memory, beginning with the most recent.
Be sure to write down any trouble codes
you find.
For every trouble code, the Service Manual
New Select Monitor - “DiagnosticCode($
Display” Selected
provides a step-by-step troubleshooting
New Select Monitor - ABS Trouble
procedure.
-
Code Displayed
Typical Troubleshooting
Procedure
AJ: TROUBLE CODE 56 DETECTION OF 0 SENSOR STICK
- DETECTION OF G SENSOR STICK -
DIAGNOSIS:
Faulty G sensor output voltage
TROUBLE SYMPTOM
ABS does not operate.
WIRING DIAGRAM:
Video Reference Booklet 71

AN INTRODUCTION TO
ABS 5.3 SYSTEM DIAGNOSIS
ABS warning light
:omes on.
gnition key position
hing
-
Before beginning diagnosis, this Chart
directs you to ask the customer when and
how the problem occurred. To assist the
service advisor with gathering the informa-
tion needed, the Service Manual provides a
list of additional interview questions. The
service advisor should ask these questions,
and write down all the information the cus-
tomer provides.
L? Always
Sometimes
Only once
0 Does not come on
0 When I how long does it come on?
LOCK
0 ACC
0 ON (before starting engine)
START
On after starting (Engine is running)
On after starting (Engine is stopped)
Immediately after ignition is ON
0 Immediately after ignition starts
When advancing krnlh to kmlh
MPHto MPI-
0 While traveling at a constant speed km/h I MPI-
0 When decelerating km/h to km/t
MPHto MPF
OWhen turning
to right Steering angle : deg
Steering time
: sec
When turning to left Steering angle : deg
Steering time
: sec
When moving other electrical parts
0 Parts name :
-ition : /
Next, the Chart directs you to perform a
pre-inspection on the vehicle, to verify that
the problem exists, and to check for any
obvious causes, such as low battery volt-
age, low brake fluid, brake drag, a worn
brake pad or rotor, or tire problems.
The pre-inspection also includes a check of
the
ABS electrical system: turn the igni-
tion switch from “Off’to “On.” If the
ABS
warning light does not come on or comes
on and stays on, there is an electrical prob-
lem.
B: CHECK LIST FOR INTERVIEW
Check The Following Items About The Vehicle’s State.
1. THE STATE OF THE ABS WARNING LIGHT
Check List for Interview
Video Reference Booklet 13

AN INTRODUCTION TO
ABS 5.3 SYSTEM DIAGNOSIS
11. General Diagnostics Table
A: SYMPTOMS AND PROBABLE CAUSES
Vehicle pulls to either side.
‘ehicle instability during braking
Vehicle spins
Long brak1ngIstoppingdis-
tance
Wheel locks.
~~
Probablefaulty unitsipam
a ABSCMBHIU (solenoidvalve)
a ABS sensor
a Brake (caliper 8. piston, pads)
a Wheel alignment
a Tire specifications,tire wear and air pressures
Incorrectwiring or piping connections
a Roadsurface (uneven,camber)
a ABSCMBHIU (solenoidvalve)
ABS sensor
a Brake (pads)
a Tire specifications,tire wear and air pressures
a Incorrectwiring or piping connections
a ABSCMBHIU (solenoid valve)
Brake (pads)
Air in brakeline
lirespecifications,tire wear and air Dressures
a Incorrectwiring or piping connections
ABSCMBHIU (solenoid valve. motor)
a ABS sensor
a Incorrectwiring or piping connections
a
ABSCMBH/U (solenoid valve) I
I
ABS sensor
a Mastercviinder
GeneralDiagnosticsTable
If there are one or more trouble codes
stored, the Chart directs you to retrieve
them using the Select Monitor, and perform
your diagnosis using the procedure speci-
fied for the trouble codes found, making
the appropriate repairs.
If there are no trouble codes, the Chart
directs you to continue your inspection
using the “General Diagnostics Table” at
the end of Section
4-4.
New Select Monitor - “Clear Memory”Selected
14 Video Reference Booklet
After you have finished your repair, the Chart
tells you to clear the trouble codes from
memory using the New Select Monitor, then
road test the vehicle and see if any new trou-
ble codes are set.
If a new trouble code is set, the Chart tells
you to diagnose the problem according to the
trouble code diagnostic procedures in the
Service Manual.
When there are no more trouble codes, the
Chart directs you to confirm that your repair
has fixed the problem, and that the
ABS
warning light does not come back on.
Using the New Select Monitor for
Diagnosis
Not only does the New Select Monitor allow
you to read trouble codes, it also helps with
diagnosis. For example, let’s assume the
vehicle has a trouble code
56 - Detection of
G-Sensor Stick. Note that the New Select
Monitor doesn’t just tell you the code num-
ber
- it also tells you which one of the four
possible problems has caused the
ABS con-
trol module to set Code
56.

AN INTRODUCTION TO
ABS 5.3 SYSTEM DIAGNOSIS
The Service Manual, Part T,
“Troubleshooting,” Section
4-4 provides
the diagnostic procedure for trouble code
56, Detection of G-Sensor Stick. Be sure
you’re looking at the diagnostic procedure
for the actual problem in this case; there
are three other diagnostic procedures for
trouble code
56!
Whenever a trouble code is set, the ABS
5.3 system stores the values of its inputs
and outputs. Before going further with the
diagnostic procedure, you can look at the
data display and see what the values were,
at the time the trouble code was set.
To do this, select “Each System Check,” as
before. then select “ABS/TCS.”
When the New Select Monitor asks
whether the vehicle has all-wheel drive and
automatic transmission, if the vehicle is
equipped with automatic transmission,
press the “Yes” button.
Now, select option
#5, “Freeze Frame
Data.”
New Select Monitor - “FreezeFrame
Data”Selected
From the Freeze Frame Menu, select “Data
Display.” The New Select Monitor will
now give you values for
11 different para-
meters at the time the DTC was set. In this
example, Code
56, you would at least want
to know what the G-sensor voltage was,
when the code was set.
You would also
want to take note of any other values that
are unusual.
Example of a Troubleshooting
Procedure
Let’s look at the troubleshooting procedure
described in the Service Manual for Code
56 - Detection of G-Sensor Stick. As a first
step, the diagnostic procedure directs you
to “check all four wheels for free turning.”
It asks, “Have the wheels been turning
freely, such as when the vehicle is lifted
up?” If
so, it tells you the system is normal
- you shouldjust erase the trouble code.
New Select Monitor - “CurrentData Display
and Save”Selected
If not, the procedure tells you to use the
Select Monitor to check the voltage output
of the G sensor. Select Option
1, “Current
Data Display and Save” and use it to read
the G-sensor voltage. Depending
on
whether the voltage reading is correct or
not, you would then troubleshoot the sen-
sor or the circuit, following the diagnostic
procedure in the Service Manual.
By the way, when the diagnostic procedure
tells you to check a connector, pay particu-
lar attention to it.
Video Reference Booklet 15

AN INTRODUCTION TO
ABS 5.3 SYSTEM DIAGNOSIS
Diagnosis Without the New Select
Monitor
In addition to diagnosis using the Select
Monitor, the Service Manual also provides
a procedure for diagnosis of the ABS
5.3
without the Select Monitor. In this case,
with the ignition switch “Off,” you would
ground terminal
6 of the diagnosis connec-
tor, using one of its grounding wires; turn
the ignition switch to “On”; and count the
ABS warning light blink codes. Then fol-
low the procedure outlined in “Diagnostics
Chart for On-board Diagnosis System.”
DiagnosisConnector - Pin 4% Grounded
Usingthe Trigger Option
One of the most useful features of the New
Select Monitor is the trigger option. When
you’re troubleshooting an intermittent
problem, this feature can be particularly
useful, if you can duplicate the problem.
The ABS control unit stores the values of
the parameters at the moment a trouble
code is set, in its internal memory. The
New Select Monitor, however, can store
data on the parameters before, during, and
after a trouble code is set.
From the Main Menu, select
“2. Each
System Check.”
From the System Selection Menu select
“ABS/TCS
.”
The New Select Monitor will now ask you
whether the vehicle has automatic trans-
mission (“ABSAWD AT”) Press “Yes.”
To set up the New Select Monitor for the
Trigger option, select “1. Current Data
Display and Save,” at the “ABS Diagnosis”
menu. At the Data Display Menu select
“12 Data Display.” The system will now
display the ABS parameters.
New Select Monitor - ABS Parameters
and Trigger Option
Using the S or “scroll” key, scroll the lower
command line
so that the Trigger option
appears. Select the Trigger option, using
the F2 key.
New Select Monitor Keypad
16 Video Reference Booklet

AN INTRODUCTION TO
ABS 5.3 SYSTEM DIAGNOSIS
Next, set up the Trigger. At the Trigger
Set-Up Menu, set the New Select Monitor
so it captures data when a code is set. At
the “Trigger” line, highlight “Code,” using
the right arrow key, then press the down
arrow key to enter this selection.
Set the Display Point at “1/2,” so that the
point when the trouble code was set will be
displayed in the middle of the screen.
Set the Time Delay so that the New Select
Monitor will continue monitoring data for
an additional 30 seconds after the code was
set. This will allow you to see what the
values of the parameters were during the
period before the trouble code was set,
until 30 seconds after. Press the “Yes” key
when you have finished setting up the
Trigger function.
New Select Monitor - Trigger Set-Up Menu
Press “C” to return to the Data Display
Menu. Press “C” again to get to the ABS
Diagnosis Menu.
Now, at the “Current Data Display and
Save” menu, select
“12. Data Display” and
then select the parameters whose values
you want to save when the trouble code is
set, using the “Yes” key and the down
arrow key to indicate the parameters you
want. You can set the New Select Monitor
to save data on up to
16 parameters. Use
the Select key (F2) to activate the Trigger
mode.
Drive the car on the road and duplicate the
conditions under which the trouble code
was set. The New Select Monitor will beep
when it has stopped recording.
New Select Monitor - Data Displayed Before,
During, and After Trouble Code Was Set
For example, the New Select Monitor
might show that a trouble code was set
when the wheel speeds were increasing, but
the G-sensor voltage remained the same,
2.3
1 volts. Ordinarily, G-sensor voltage
should drop below 2.3 volts when the car is
accelerating, and should rise above 2.3
when the car is decelerating. Using this
information, you could then troubleshoot
the sensor and the circuit to see why the
voltage remained constant.
Video Reference Booklet 17

AN INTRODUCTION TO
ABS 5.3 SYSTEM DIAGNOSIS
You will need to perform the brake bleed-
ing procedure any time air gets into the
system or after major service is performed,
such as replacing the HCU or the master
cylinder.
When bleeding the brakes, be sure to fol-
low all the cautions and notes in the
Service Manual, Part W, “Service
Procedures,” Section
4-4.
First, bleed the brakes the conventional
way, in the order specified in the Service
Manual. Put one end of a vinyl tube on the
air bleeder port and the other end into a
container of brake fluid.
Setup for Bleeding Brakes
Have a helper slowly depress the brake
pedal and keep it depressed, while you
open the air bleeder for
1 to 2 seconds.
Then close the bleeder and slowly release
the brake pedal. After
3 to 4 seconds
repeat the procedure. Continue in this
fashion until there are no more air bubbles
in the fluid flowing out of the brake.
Then tighten the bleeder screw to a torque
of
5.8 +/- 0.7 ft.lb. (8 +/- 1 N-m).
When all four brakes have been bled,
depress the brake pedal and keep it in that
position for about
20 seconds to make sure
there is no leak in the system. Then pro-
ceed to Sequence Control.
Sequence Control
With an ABS system, once you have bled
the brakes in the conventional way, you
have to activate Sequence Control to push
air out of the HCU into the brake lines.
Otherwise, air trapped in the HCU will get
into the lines and the customer may return,
complaining that the brakes have become
“spongy.” During Sequence Control, the
HCU turns on the motor-pump assembly
and commands Pressure Decrease, Pressure
Hold, and Pressure Increase for each
caliper.
Using the New Select Monitor, command
Sequence Control, as follows. At the “ABS
Diagnosis” menu, select
“4. Function
Check Sequence” and follow the directions
displayed on the New Select Monitor’s
screen. Command Sequence Control
twice, in order to ensure that you have
expelled all air from the HCU. Then bleed
the brakes again, the conventional way, to
remove any air pushed out of the HCU into
the brake lines.
New Select Monitor - “Function Check
Sequence” Selected
18 Video Reference Booklet

AN INTRODUCTION TO
ABS 5.3 SYSTEM DIAGNOSIS
Checkingthe Pedal Stroke
Now, check the pedal stroke. With the
engine idling, depress the brake pedal with
the brake pedal effort gauge, at
110 lb. of
force, and measure the distance between
the brake pedal and the steering wheel.
Turn the ignition switch “On” and, within a
half second after the ABS warning light
goes off, depress the brake pedal and hold
it. The ABS will go into Sequence Control
and purge air from the HCU.
Release the brake pedal and measure it
again. For a vehicle with ABS, brake pedal
travel should not exceed 3 3/4 in. (95 mm).
If the travel is more than that, there may
still be some air inside the HCU. Perform
the brake bleeding procedure again, using
Sequence Control and conventional bleed-
ing.
Using the Brake Pedal Effort
Gauge to MeasureTravel
When bleeding is complete, add brake fluid
to the required level indicated on the brake
fluid reservoir by the line labeled “MAX.”
Finally, road test the vehicle at a low speed
and apply the brakes hard, two or three
times, to ensure that they work properly.
Commanding Sequence Control
Without the Select Monitor
You can also command Sequence Control
without the Select Monitor. To do this,
with the ignition switch “Off,” ground ter-
minals 3 and
6 of the diagnosis connector,
using the connector’s grounding wires.
CONCLUSION
Effective diagnosis requires a logical, step-
by-step approach. Be sure to use the
appropriate Service Manual, the New
Select Monitor, and this Video Reference
Booklet to look for trouble codes, perform
diagnosis, and bleed air from the system.
That way, you should have no trouble with
the ABS 5.3.
Video Reference Booklet 19