Subaru Legacy III (2000-2003 year). Service manual — part 732

ABS-146

ABS (DIAGNOSTICS)

DIAGNOSTICS CHART WITH SUBARU SELECT MONITOR

AH:DTC 56 DETECTION OF G SENSOR STICK

DIAGNOSIS:
• Faulty G sensor output voltage
TROUBLE SYMPTOM:
• ABS does not operate.
WIRING DIAGRAM:

ABS00312

F55

R70

F62

ABS CONTROL MODULE AND
HYDRAULIC CONTROL UNIT

ABS

G SENSOR

F49

2

1

3

F49

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

16 17 18 19 20 21 22

27 28 29 30 31

23

24

25

26

3

7

6

28

1

2

3

F55

R49

R70

2

8

30

1

2 3

4 5 6 7 8

ABS-147

ABS (DIAGNOSTICS)

DIAGNOSTICS CHART WITH SUBARU SELECT MONITOR

Step

Value

Yes

No

1

CHECK WHEELS FOR FREE TURNING.
Have the wheels been turned freely such as
when the vehicle is lifted up, or operated on a
rolling road?

Wheel have not turned freely.

Go to step 2.

The ABS is nor-
mal. Erase the
trouble code.

2

CHECK OUTPUT OF G SENSOR USING SE-
LECT MONITOR.
1) Select “Current data display & Save” on the

select monitor.

2) Read the select monitor display.

Is the G sensor output on the monitor dis-
play within the specified range when the
vehicle is in horizontal position?

2.1 - 2.5 V

Go to step 3.

Go to step 8.

3

CHECK OUTPUT OF G SENSOR USING SE-
LECT MONITOR.
1) Turn ignition switch to OFF.
2) Remove console box.
3) Remove G sensor from vehicle. (Do not

disconnect connector.)

4) Turn ignition switch to ON.
5) Select “Current data display & Save” on the

select monitor.

6) Read the select monitor display.

Is the G sensor output on the monitor dis-
play within the specified range when G
sensor is inclined forwards to 90

°

?

3.7 - 4.1 V

Go to step 4.

Replace G sen-
sor. <Ref. to ABS-
21, G Sensor.>

4

CHECK OUTPUT OF G SENSOR USING SE-
LECT MONITOR.
Read the select monitor display.
Is the G sensor output on the monitor display
within the specified range when G sensor is
inclined backwards to 90

°

?

0.5 - 0.9 V

Go to step 5.

Replace G sen-
sor. <Ref. to ABS-
21, G Sensor.>

5

CHECK POOR CONTACT IN CONNECTORS.
Turn ignition switch to OFF.
Is there poor contact in connector between
ABSCM&H/U and G sensor?

There is no poor contact.

Go to step 6.

Repair connector.

6

CHECK ABSCM&H/U.
1) Connect all connectors.
2) Erase the memory.
3) Perform inspection mode.
4) Read out the DTC.

Is the same DTC still being output?

Same DTC is not indicated.

Go to step 7.

Replace
ABSCM&H/U.
<Ref. to ABS-6,
ABS Control Mod-
ule and Hydraulic
Control Unit
(ABSCM&H/U).>

7

CHECK ANY OTHER DTC APPEARANCE.
Are other DTC being output?

Other DTC is not indicated.

A temporary poor
contact.

Proceed with the
diagnosis corre-
sponding to the
DTC.

8

CHECK OPEN CIRCUIT IN G SENSOR OUT-
PUT HARNESS AND GROUND HARNESS.
1) Turn ignition switch to OFF.
2) Disconnect connector from ABSCM&H/U.
3) Measure resistance between ABSCM&H/U

connector terminals.

Connector & terminal

(F49) No. 6 — No. 28:

Is the measured value within the specified
range?

5.0 - 5.6 k

Ω

Go to step 9.

Repair harness/
connector
between G sensor
and ABSCM&H/U.

ABS-148

ABS (DIAGNOSTICS)

DIAGNOSTICS CHART WITH SUBARU SELECT MONITOR

9

CHECK G SENSOR.
1) Remove console box.
2) Remove G sensor from vehicle.
3) Connect connector to G sensor.
4) Connect connector to ABSCM&H/U.
5) Turn ignition switch to ON.
6) Measure voltage between G sensor con-

nector terminals.

Connector & terminal

(R70) No. 2 (+) — No. 3 (

−−−−

):

Is the voltage within the specified range
when G sensor is horizontal?

2.1 - 2.5 V

Go to step 10.

Replace G sen-
sor. <Ref. to ABS-
21, G Sensor.>

10

CHECK G SENSOR.
Measure voltage between G sensor connector
terminals.

Connector & terminal

(R70) No. 2 (+) — No. 3 (

−−−−

):

Is the voltage within the specified range when
G sensor is inclined forwards to 90

°

?

3.7 - 4.1 V

Go to step 11.

Replace G sen-
sor. <Ref. to ABS-
21, G Sensor.>

11

CHECK G SENSOR.
Measure voltage between G sensor connector
terminals.

Connector & terminal

(R70) No. 2 (+) — No. 3 (

−−−−

):

Is the voltage within the specified range when
G sensor is inclined backwards to 90

°

?

0.5 - 0.9 V

Go to step 12.

Replace G sen-
sor. <Ref. to ABS-
21, G Sensor.>

12

CHECK ABSCM&H/U.
1) Turn ignition switch to OFF.
2) Connect all connectors.
3) Erase the memory.
4) Perform inspection mode.
5) Read out the DTC.

Is the same DTC still being output?

Same DTC is not indicated.

Go to step 13.

Replace
ABSCM&H/U.
<Ref. to ABS-6,
ABS Control Mod-
ule and Hydraulic
Control Unit
(ABSCM&H/U).>

13

CHECK ANY OTHER DTC APPEARANCE.
Are other DTC being output?

Other DTC is not indicated.

A temporary poor
contact.

Proceed with the
diagnosis corre-
sponding to the
DTC.

Step

Value

Yes

No

ABS-149

ABS (DIAGNOSTICS)

GENERAL DIAGNOSTICS TABLE

14.General Diagnostics Table

A: INSPECTION

Symptom

Probable faulty units/parts

Vehicle instability during braking

Vehicle pulls to either side.

• ABSCM&H/U (solenoid valve)
• ABS sensor
• Brake (caliper & piston, pads)
• Wheel alignment
• Tire specifications, tire wear and air pressures
• Incorrect wiring or piping connections
• Road surface (uneven, camber)

Vehicle spins.

• ABSCM&H/U (solenoid valve)
• ABS sensor
• Brake (pads)
• Tire specifications, tire wear and air pressures
• Incorrect wiring or piping connections

Poor braking

Long braking/stopping distance

• ABSCM&H/U (solenoid valve)
• Brake (pads)
• Air in brake line
• Tire specifications, tire wear and air pressures
• Incorrect wiring or piping connections

Wheel locks.

• ABSCM&H/U (solenoid valve, motor)
• ABS sensor
• Incorrect wiring or piping connections

Brake dragging

• ABSCM&H/U (solenoid valve)
• ABS sensor
• Master cylinder
• Brake (caliper & piston)
• Parking brake
• Axle & wheels
• Brake pedal play

Long brake pedal stroke

• Air in brake line
• Brake pedal play

Vehicle pitching

• Suspension play or fatigue (reduced damping)
• Incorrect wiring or piping connections
• Road surface (uneven)

Unstable or uneven braking

• ABSCM&H/U (solenoid valve)
• ABS sensor
• Brake (caliper & piston, pads)
• Tire specifications, tire wear and air pressures
• Incorrect wiring or piping connections
• Road surface (uneven)

Vibration and/or noise
(while driving on slippery roads)

Excessive pedal vibration

• Incorrect wiring or piping connections
• Road surface (uneven)

Noise from ABSCM&H/U

• ABSCM&H/U (mount bushing)
• ABS sensor
• Brake piping

Noise from front of vehicle

• ABSCM&H/U (mount bushing)
• ABS sensor
• Master cylinder
• Brake (caliper & piston, pads, rotor)
• Brake piping
• Brake booster & check valve
• Suspension play or fatigue

Noise from rear of vehicle

• ABS sensor
• Brake (caliper & piston, pads, rotor)
• Parking brake
• Brake piping
• Suspension play or fatigue