Subaru 2009 IMPREZA Service Manual page 620

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
6 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
rear oxygen sensor.
3) Measure the resistance of harness between
ECM and rear oxygen sensor connector.
Connector & terminal
(B135) No. 4 — (E23) No. 3:
(B134) No. 29 — (E23) No. 4:
7 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between rear oxygen
sensor connector and chassis ground.
Connector & terminal
(E23) No. 3 (+) — Chassis ground (–):
8 CHECK REAR OXYGEN SENSOR SHIELD.
1) Turn the ignition switch to OFF.
2) Expose the rear oxygen sensor connector
body side harness sensor shield.
3) Measure the resistance between sensor
shield and chassis ground.
Check
Is the resistance less than 1 ? Go to step 7.
Is the voltage 0.2 — 0.5 V?
Is the resistance less than 1 ? Replace the rear
EN(H4SO)(diag)-203
ENGINE (DIAGNOSTICS)
Yes No
Repair the harness
and connector.
NOTE:
Repair the follow-
ing locations.
• Open circuit in
harness between
ECM and rear oxy-
gen sensor con-
nector
• Poor contact of
coupling connector
Go to step 8. Repair the harness
and connector.
NOTE:
Repair the follow-
ing locations.
• Open circuit in
harness between
ECM and rear oxy-
gen sensor con-
nector
• Poor contact of
ECM connector
• Poor contact of
coupling connector
Repair the open
oxygen sensor. circuit of rear oxy-
<Ref. to gen sensor har-
FU(H4SO)-43, ness.
Rear Oxygen Sen-
sor.>