Subaru IMPREZA GD 2007 Series Manual page 198

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Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
1 CHECK POWER SUPPLY TO REAR OXY-
GEN SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from the rear oxy-
gen sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between rear oxygen
sensor connector and engine ground.
Connector & terminal
(E119) No. 2 (+) — engine ground (–):
2 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from the ECM.
3) Measure the resistance between ECM and
rear oxygen sensor connector.
Connector & terminal
(B136) No. 4 — (E119) No. 1:
3 CHECK GROUND CIRCUIT FOR ECM.
Measure the resistance of harness between
ECM and chassis ground.
Connector & terminal
(B134) No. 5 — Chassis ground:
(B137) No. 1 — Chassis ground:
(B137) No. 2 — Chassis ground:
(B137) No. 3 — Chassis ground:
(B137) No. 7 — Chassis ground:
4 CHECK REAR OXYGEN SENSOR.
Measure the resistance between rear oxygen
sensor connector terminals.
Terminals
No. 2 — No. 1:
Check
Is the voltage 10 V or more?
Is the resistance less than 1 Ω? Go to step 3.
Is the resistance less than 5 Ω? Go to step 4.
Is the resistance between 5 —
7 Ω?
EN(H4SO)(diag)-89
ENGINE (DIAGNOSTICS)
Yes No
Go to step 2. Repair the power
supply line or
replace the main
relay.
NOTE:
In this case, repair
the following item:
• Open circuit of
the harness be-
tween A/F oxygen
sensor relay and
rear oxygen sen-
sor
• Poor contact of
A/F & oxygen sen-
sor relay connector
• Poor contact in
coupling connector
Repair the open
circuit of the har-
ness between
ECM and rear oxy-
gen sensor.
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
• Open circuit of
harness between
ECM and engine
ground
• Poor contact in
ECM connector
• Poor contact of
coupling connector
Repair poor con- Replace the rear
tact of the ECM oxygen sensor.
connector. <Ref. to
FU(H4SO)-37,
Rear Oxygen Sen-
sor.>