Subaru Legacy 2004 Service Manual page 1354

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
1 CHECK GROUND CIRCUIT FOR ECM.
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
(B135) No. 1 — Chassis ground:
(B135) No. 4 — Chassis ground:
2 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR.
1) Disconnect the connector from rear oxygen
sensor.
2) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B135) No. 2 — Chassis ground:
3 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B135) No. 2 — Chassis ground:
4 CHECK POWER SUPPLY TO REAR OXY-
GEN SENSOR.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between rear oxygen
sensor connector and chassis ground.
Connector & terminal
(T6) No. 1 (+) — Chassis ground (
Check
Is the resistance less than 5
'?
Is the voltage more than 1
M'?
Does the resistance change by
shaking the ECM harness and
connector?
Is the voltage more than 10 V? Go to step 5.
"
):
EN(H4DOTC)(diag)-65
ENGINE (DIAGNOSTICS)
Yes
Go to step 2. Repair the har-
ness and connec-
tor.
NOTE:
In this case, repair
the following:
• Open circuit in
harness between
ECM and engine
ground cable
• Poor contact in
ECM connector
• Poor contact in
coupling connector
Go to step 3. Repair the ground
short circuit in har-
ness between
ECM and rear oxy-
gen sensor con-
nector.
Repair the poor Go to step 4.
contact in ECM
connector.
Repair the power
supply line.
NOTE:
In this case, repair
the following:
• Open circuit in
harness between
main relay and
rear oxygen sen-
sor connector
• Poor contact in
rear oxygen sen-
sor connector
• Poor contact in
coupling connector
No