Subaru Impreza 2003 Service Manual page 2395

DIAGNOSTICS PROCEDURE WITHOUT DIAGNOSTIC TROUBLE CODE (DTC)
Step
2 CHECK ABS WHEEL SPEED SENSOR GAP.
Measure the tone wheel to ABS wheel speed
sensor piece gap over entire perimeter of the
wheel.
3 PREPARE OSCILLOSCOPE.
4 CHECK ABS WHEEL SPEED SENSOR SIG-
NAL.
1)Raise all four wheels off ground.
2)Turn the ignition switch to OFF.
3)Connect the oscilloscope to the connector.
4)Turn the ignition switch to ON.
5)Rotate the wheels and measure voltage at
specified frequency. <Ref. to ABS-16, WAVE-
FORM, Control Module I/O Signal.>
NOTE:
When this inspection is completed, the ABS
control module sometimes stores DTC 29 or
DTC 56.
Connector & terminal
DTC 22
LHD: (B15) No. 1 (+) — No. 2 ( − − − − ):
RHD: (F95) No. 1 (+) — No. 2 ( − − − − ):
DTC 24
LHD: (F45) No. 20 (+) — No. 24 ( − − − − ):
RHD: (F94) No. 1 (+) — No. 2 ( − − − − ):
DTC 26
LHD: (B99) No. 10 (+) — No. 9 ( − − − − ):
RHD: (B99) No. 32 (+) — No. 31 ( − − − − ):
DTC 28
LHD: (B99) No. 5 (+) — No. 4 ( − − − − ):
RHD: (B99) No. 20 (+) — No. 21 ( − − − − ):
5 CHECK CONTAMINATION OF ABS WHEEL
SPEED SENSOR OR TONE WHEEL.
Remove the disc rotor or drum from hub in
accordance with DTC.
6 CHECK DAMAGE OF ABS WHEEL SPEED
SENSOR OR TONE WHEEL.
Check
Is the gap as following value?
Front wheel:
0.3 — 0.8 mm (0.012 — 0.031
in)
Rear wheel
0.7 — 1.2 mm (0.028 — 0.047
in)
Is an oscilloscope available?
Is an oscilloscope pattern
smooth, as shown in the fig-
ure?
Is the ABS wheel speed sen-
sor piece or the tone wheel
contaminated by dirt or other
foreign matter?
Are there broken or damaged
in the ABS wheel speed sen-
sor piece or the tone wheel?
ABS-55
ABS (DIAGNOSTICS)
Yes
Go to step 3. Adjust the gap.
NOTE:
Adjust the gap us-
ing spacer (Part
No. 26755AA000).
If the spacer can-
not correct gap, re-
place worn sensor
or worn
wheel.
Go to step 4. Go to step 5.
Go to step 8. Go to step 7.
Thoroughly Go to step 6.
remove dirt or
other foreign mat-
ter.
Replace the ABS Go to step 7.
wheel speed sen-
sor or tone wheel.
Front: <Ref. to
ABS-13, Front
ABS Wheel Speed
Sensor.> Rear:
<Ref. to ABS-16,
Rear ABS Wheel
Speed Sensor.>
and Front: <Ref. to
ABS-19, Front
Tone Wheel.>
Rear: <Ref. to
ABS-20, Rear
Tone Wheel.>
No
tone