Subaru Legacy III (2000-2003 year). Service manual — part 504
EN(H4DOSTC)-186
ENGINE (DIAGNOSTICS)
DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
AT: DTC P1131 — O2 SENSOR CIRCUIT (SHORT) (BANK1 SENSOR1) —
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H4DOSTC)-35,
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4DOSTC)-33, Inspection
Mode.> .
• WIRING DIAGRAM:
EN-00933
BATTERY
MAIN RELAY
SBF-5
B47
1
2
3
5
4
6
E
E
E3
3
8
9
4
5
19
29
18
ECM
B137
B22
2
4
1
3
B18
FRONT OXYGEN
(A/F) SENSOR
3 4
1 2
3
4
1
2
5
6
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16
B22
B47
B18
B137
1
2
7
8
9
5
6
3
4
10 11 12
19 20 21
29 30 31
13 14 15 16 17
27 28
18
22 23 24 25 26
EN(H4DOSTC)-187
ENGINE (DIAGNOSTICS)
DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
Value
Yes
No
1
CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness
between ECM connector and chassis
ground.
Connector & terminal
(B137) No. 19 — Chassis ground:
Does the measured value exceed the spec-
ified value?
1 M
Ω
Repair the ground
short circuit in har-
ness between
ECM and front
oxygen (A/F) sen-
sor connector.
2
CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
Measure the resistance of harness between
ECM connector and chassis ground.
Connector & terminal
(B137) No. 29 — Chassis ground:
Does the measured value exceed the specified
value?
1 M
Ω
Repair the ground
short circuit in har-
ness between
ECM and front
oxygen (A/F) sen-
sor connector.
3
CHECK OUTPUT SIGNAL FOR ECM.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between ECM con-
nector and chassis ground.
Connector & terminal
(B137) No. 19 (+) — Chassis ground (
−−−−
):
Does the measured value exceed the spec-
ified value?
4.5 V
4
CHECK OUTPUT SIGNAL FOR ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B137) No. 19 (+) — Chassis ground (
−−−−
):
Does the measured value exceed the specified
value?
10 V
Repair the battery
short circuit in har-
ness between
ECM and front
oxygen (A/F) sen-
sor connector.
After repair,
replace the ECM.
<Ref. to
FU(H4DOSTC)-
40, Engine Con-
trol Module.>
Repair the poor
contact in ECM
connector.
5
CHECK OUTPUT SIGNAL FOR ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B137) No. 29 (+) — Chassis ground (
−−−−
):
Does the measured value exceed the specified
value?
4.95 V
Replace the front
oxygen (A/F) sen-
sor. <Ref. to
FU(H4DOSTC)-
38, Front Oxygen
(A/F) Sensor.>
EN(H4DOSTC)-188
ENGINE (DIAGNOSTICS)
DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
6
CHECK OUTPUT SIGNAL FOR ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B137) No. 29 (+) — Chassis ground (
−−−−
):
Does the measured value exceed the specified
value?
10 V
Repair the battery
short circuit in har-
ness between
ECM and front
oxygen (A/F) sen-
sor connector.
After repair,
replace the ECM.
<Ref. to
FU(H4DOSTC)-
40, Engine Con-
trol Module.>
Repair the poor
contact in ECM
connector.
Step
Value
Yes
No
EN(H4DOSTC)-189
ENGINE (DIAGNOSTICS)
DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
MEMO:
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