Subaru Legacy 2002 Service Manual page 1363

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Engine (DIAGNOSTICS)
No.
1 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn ignition switch to OFF.
2) Disconnect connector from ECM.
3) Measure resistance of harness between
ECM connector and chassis ground.
Connector & terminal
(B137) No. 19 — Chassis ground:
2 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
Measure resistance of harness between ECM
connector and chassis ground.
Connector & terminal
(B137) No. 29 — Chassis ground:
3 CHECK OUTPUT SIGNAL FOR ECM.
1) Connect connector to ECM.
2) Turn ignition switch to ON.
3) Measure voltage between ECM connector
and chassis ground.
Connector & terminal
(B137) No. 19 (+) — Chassis ground
(−):
4 CHECK OUTPUT SIGNAL FOR ECM.
Measure voltage between ECM connector
and chassis ground.
Connector & terminal
(B137) No. 19 (+) — Chassis ground
(−):
5 CHECK OUTPUT SIGNAL FOR ECM.
Measure voltage between ECM connector
and chassis ground.
Connector & terminal
(B137) No. 29 (+) — Chassis ground
(−):
6 CHECK OUTPUT SIGNAL FOR ECM.
Measure voltage between ECM connector
and chassis ground.
Connector & terminal
(B137) No. 29 (+) — Chassis ground
(−):
Step
Is the resistance more than
10 Ω?
Is the resistance more than
10 Ω?
Is the voltage more than
4.5 V?
Is the voltage more than 10
V?
Is the voltage more than
4.95 V?
Is the voltage more than 10
V?
EN(H6)-156
Check Yes
Go to step 2.
Go to step 3.
Go to step 4.
Repair battery
short circuit in
harness between
ECM and front
oxygen (A/F) sen-
sor connector.
After repair,
replace ECM.
<Ref. to FU(H6)-
47, Engine Con-
trol Module.>
Go to step 6.
Repair battery
short circuit in
harness between
ECM and front
oxygen (A/F) sen-
sor connector.
After repair,
replace ECM.
<Ref. to FU(H6)-
47, Engine Con-
trol Module.>
No
Repair ground
short circuit in
harness between
ECM and front
oxygen (A/F) sen-
sor connector.
Repair ground
short circuit in
harness between
ECM and front
oxygen (A/F) sen-
sor connector.
Go to step 5.
Repair poor con-
tact in ECM con-
nector.
Replace front oxy-
gen (A/F) sensor.
<Ref. to FU(H6)-
43, Front Oxygen
(A/F) Sensor.>
Repair poor con-
tact in ECM con-
nector.