Subaru IMPREZA GD 2007 Series Manual page 391

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Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed?
2 CHECK FRONT OXYGEN (A/F) SENSOR
CONNECTOR AND COUPLING CONNEC-
TOR.
3 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from the ECM
and front oxygen (A/F) sensor.
3) Measure the resistance of harness between
ECM and front oxygen (A/F) sensor connector.
Connector & terminal
(B135) No. 9 — (E118) No. 1:
(B135) No. 8 — (E118) No. 3:
4 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
Measure the resistance between ECM and
chassis ground.
Connector & terminal
(B135) No. 9 — Chassis ground:
(B135) No. 8 — Chassis ground:
5 CHECK OUTPUT SIGNAL FOR ECM.
1) Connect the ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between front oxygen
(A/F) sensor connector and chassis ground.
Connector & terminal
(E118) No. 1 (+) — Chassis ground (–):
6 CHECK OUTPUT SIGNAL FOR ECM.
Measure the voltage between front oxygen (A/
F) sensor connector and chassis ground.
Connector & terminal
(E118) No. 3 (+) — Chassis ground (–):
Check
Has water entered the connec-
tor?
Is the resistance less than 1 Ω? Go to step 4.
Is the resistance 1 MΩ or
more?
Is the voltage 4.5 V or more?
Is the voltage 4.95 V or more? Go to step 7.
EN(H4SO)(diag)-282
Yes No
Check DTC using Go to step 2.
"List of Diagnostic
Trouble Code
(DTC)". <Ref. to
EN(H4SO)(diag)-
72, List of Diagnos-
tic Trouble Code
(DTC).>
Go to step 3.
Completely
remove any water
inside.
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
• Open circuit in
harness between
ECM and front oxy-
gen (A/F) sensor
connector
• Poor contact in
front oxygen (A/F)
sensor connector
• Poor contact in
ECM connector
• Poor contact of
coupling connector
Go to step 5.
Repair short cir-
cuit of the harness
to ground between
ECM and front oxy-
gen (A/F) sensor
connector.
Go to step 7. Go to step 6.
Go to step 8.