Subaru Legacy 2003 Service Manual page 488

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
1 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Start and warm-up engine.
2) Turn ignition switch to OFF.
3) Disconnect connectors from ECM and front
oxygen (A/F) sensor.
4) Measure harness resistance between ECM
and front oxygen (A/F) sensor connector.
Connector & terminal
(B136) No. 6 - (B18) No. 3:
(B136) No. 17 - (B18) No. 3:
Is the measured value less than the speci-
fied value?
2 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
Measure harness resistance between ECM
and front oxygen (A/F) sensor connector.
Connector & terminal
(B136) No. 13 - (B18) No. 1:
(B136) No. 22 - (B18) No. 2:
Is the measured value less than the specified
value?
3 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
Measure harness resistance between main
relay and front oxygen (A/F) sensor connector.
Connector & terminal
(B47) No. 4 — (B18) No. 4:
Is the measured value less than the specified
value?
4 CHECK FRONT OXYGEN (A/F) SENSOR.
Measure resistance between terminals in front
oxygen (A/F) sensor connector.
Terminal
No.3 - No.4:
Is the measured value less than the specified
value?
5 CHECK POOR CONTACT.
Check ECM and front oxygen (A/F) sensor
connector for poor contact.
Is there any poor contact in ECM and front
oxygen (A/F) sensor connector.
Value
1 Ω
1 Ω
1 Ω
5 Ω
There is poor contact.
EN(H4SO)-91
ENGINE (DIAGNOSTICS)
Yes
Go to step 2. Repair open circuit
between ECM and
front oxygen (A/F)
sensor connector.
Go to step 3. Repair open circuit
between ECM and
front oxygen (A/F)
sensor connector.
Go to step 4. Repair open circuit
between ECM and
front oxygen (A/F)
sensor connector.
Go to step 5. Replace front oxy-
gen (A/F) sensor.
<Ref. to
FU(H4SO)-41,
Front Oxygen (A/
F) Sensor.>
Repair poor con- Replace front oxy-
tact in ECM and gen (A/F) sensor.
front oxygen (A/F) <Ref. to
sensor connector. FU(H4SO)-41,
Front Oxygen (A/
F) Sensor.>
No