Subaru Legacy III (2000-2003 year). Manual - part 730

ABS-138

ABS (DIAGNOSTICS)

DIAGNOSTICS CHART WITH SUBARU SELECT MONITOR

AF:DTC 56 BATTERY SHORT IN G SENSOR CIRCUIT

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-139

ABS (DIAGNOSTICS)

DIAGNOSTICS CHART WITH SUBARU SELECT MONITOR

Step

Value

Yes

No

1

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

select monitor.

2) Read the G sensor output in select monitor 

data display.
Is the G sensor output on the monitor dis-
play between within the specified range 
when the G sensor is in horizontal position?

 2.1 - 2.5 V

Go to step 2.

Go to step 5.

2

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

There is no poor contact.

Go to step 3.

Repair connector.

3

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 4.

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

4

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.

5

CHECK FREEZE FRAME DATA.
1) Select “Freeze frame data” on the select 

monitor.

2) Read front right wheel speed on the select 

monitor display.
Is the front right wheel speed on monitor 
display same as the specified value?

0 km/h (0 MPH)

Go to step 6.

Go to step 16.

6

CHECK FREEZE FRAME DATA.
Read front left wheel speed on the select mon-
itor display.
Is the front left wheel speed on monitor display 
same as the specified value?

0 km/h (0 MPH)

Go to step 7.

Go to step 16.

7

CHECK FREEZE FRAME DATA.
Read rear right wheel speed on the select 
monitor display.
Is the rear right wheel speed on monitor dis-
play same as the specified value?

0 km/h (0 MPH)

Go to step 8.

Go to step 16.

8

CHECK FREEZE FRAME DATA.
Read rear left wheel speed on the select moni-
tor display.
Is the rear left wheel speed on monitor display 
same as the specified value?

0 km/h (0 MPH)

Go to step 9.

Go to step 16.

9

CHECK FREEZE FRAME DATA.
Read G sensor output on the select monitor 
display.
Does measured value exceed the specified 
value on monitor display?

3.65 V

Go to step 10.

Go to step 16.

ABS-140

ABS (DIAGNOSTICS)

DIAGNOSTICS CHART WITH SUBARU SELECT MONITOR

10

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 11.

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

11

CHECK BATTERY SHORT OF HARNESS.
1) Turn ignition switch to OFF.
2) Remove console box.
3) Disconnect connector from G sensor.
4) Disconnect connector from ABSCM&H/U.
5) Measure voltage between ABSCM&H/U 

connector and chassis ground.

Connector & terminal

(F49) No. 6 (+) — Chassis ground (

−−−−

):

Is the measured value less than the speci-
fied value?

1 V

Go to step 12.

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

12

CHECK BATTERY SHORT OF HARNESS.
1) Turn ignition switch to ON.
2) Measure voltage between ABSCM&H/U 

connector and chassis ground.

Connector & terminal

(F49) No. 6 (+) — Chassis ground (

−−−−

):

Is the measured value less than the speci-
fied value?

1 V

Go to step 13.

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

13

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

There is no poor contact.

Go to step 14.

Repair connector.

14

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 15.

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

15

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.

16

CHECK INPUT VOLTAGE OF G SENSOR.
1) Turn ignition switch to OFF.
2) Remove console box.
3) Disconnect G sensor from body. (Do not 

disconnect connector.)

4) Turn ignition switch to ON.
5) Measure voltage between G sensor con-

nector terminals.

Connector & terminal

(R70) No. 1 (+) — No. 3 (

−−−−

):

Is the measured value within the specified 
range?

4.75 - 5.25 V

Go to step 17.

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

Step

Value

Yes

No

ABS-141

ABS (DIAGNOSTICS)

DIAGNOSTICS CHART WITH SUBARU SELECT MONITOR

17

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 18.

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

18

CHECK G SENSOR.
1) Connect connector to G sensor.
2) Connect connector to ABSCM&H/U.
3) Turn ignition switch to ON.
4) Measure voltage between G sensor con-

nector terminals.

Connector & terminal

(R70) No. 2 (+) — No. 3 (

−−−−

):

Is the voltage within th especified range  
when G sensor is horizontal?

2.1 - 2.5 V

Go to step 19.

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

19

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 20.

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

20

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

Connector & terminal

(R70) No. 2 (+) — No. 3 (

−−−−

):

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

°

?

0.5 - 0.9 V

Go to step 21.

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

21

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 22.

Repair connector.

22

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 23.

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

23

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