Subaru Legacy 2004 Service Manual page 3021

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ABS (DIAGNOSTICS)
Step
1 WHETHER A WHEEL TURNED FREELY OR
NOT.
Check if the wheels have been turned freely for
more than one minute, such as when the vehi-
cle is jacked-up, under full-lock cornering or
when the wheels are not in contact with road
surface.
2 CHECK TIRE SPECIFICATIONS.
Turn the ignition switch to OFF.
3 CHECK WEAR OF TIRE.
4 CHECK TIRE INFLATION PRESSURE.
5 CHECK INSTALLATION OF ABS WHEEL
SPEED SENSOR.
6 CHECK ABS WHEEL SPEED SENSOR SIG-
NAL.
1) Install the ABS wheel speed sensor.
2) Prepare an oscilloscope.
3) Check ABS wheel speed sensor. <Ref. to
ABS-13, ABS WHEEL SPEED SENSOR,
INSPECTION, Front ABS Wheel Speed Sen-
sor.>
7 CHECK ABS WHEEL SPEED SENSOR AND
MAGNETIC ENCODER.
8 CHECK ABSCM&H/U.
1) Connect all the connectors.
2) Erase the memory.
3) Perform the inspection mode. <Ref. to
ABS(diag)-17, CLEAR MEMORY MODE,
OPERATION, Subaru Select Monitor.>
4) Read the DTC.
Check
Did the wheels turn freely?
Are the tire specifications cor-
rect?
Is the tire worn excessively?
Is the tire pressure correct?
Is the ABS wheel speed sen-
sor installation bolt tightened
7.5 N'm (0.76 kgf-m, 5.5 ft-lb)?
(four of them)
Does the oscilloscope indicate
the waveform pattern like
shown in the figure when the
tire is slowly turned? Does the
oscilloscope indication repeat
the waveform pattern like
shown in the figure when the
tire is slowly turned in equal
speed for more one rotation?
Is there foreign particles,
breakage or damage in the
pole piece of ABS wheel speed
sensor or magnetic encoder?
Is the same DTC displayed?
ABS(diag)-54
Yes
ABS is normal. Go to step 2.
Erase the memory.
NOTE:
When the wheels
turn freely for a
long time, such as
when the vehicle is
towed or jacked-
up, or when steer-
ing wheel is contin-
uously turned all
the way, this diag-
nostic trouble code
may sometimes
occur.
Go to step 3. Replace the tire.
Replace the tire. Go to step 4.
Go to step 5. Adjust the tire
pressure.
Go to step 6. Tighten the ABS
wheel speed sen-
sor installation
bolts.
Go to step 8. Go to step 7.
Remove dirt com- Go to step 8.
pletely. Replace
the ABS wheel
speed sensor or
magnetic encoder
as a unit with hub
unit bearing when
it is broken or
damaged.
Replace the Go to step 9.
ABSCM only.
<Ref. to ABS-8,
REPLACEMENT,
ABS Control Mod-
ule and Hydraulic
Control Unit
(ABSCM&H/U).>
No