Subaru 2009 IMPREZA Service Manual page 695

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 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 — (E22) No. 1:
(B135) No. 8 — (E22) 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 connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between front oxygen
(A/F) sensor connector and chassis ground.
Connector & terminal
(E22) 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
(E22) No. 3 (+) — Chassis ground (–):
7 CHECK OUTPUT SIGNAL FOR ECM.
Measure the voltage between front oxygen (A/
F) sensor connector and chassis ground.
Connector & terminal
(E22) No. 1 (+) — Chassis ground (–):
(E22) No. 3 (+) — Chassis ground (–):
8 CHECK EXHAUST SYSTEM.
Check
Has water entered the connec-
tor?
Is the resistance less than 1 ? Go to step 4.
Is the resistance 1 M or
more?
Is the voltage 4.5 V or more?
Is the voltage 4.95 V or more? Go to step 7.
Is the voltage 8 V or more?
Are there holes or loose bolts
on exhaust system?
EN(H4SO)(diag)-278
Yes No
Check DTC using Go to step 2.
"List of Diagnostic
Trouble Code
(DTC)". <Ref. to
EN(H4SO)(diag)-
86, List of Diagnos-
tic Trouble Code
(DTC).>
Completely Go to step 3.
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 of
coupling connector
Go to step 5. Repair the ground
short circuit of har-
ness between
ECM and front oxy-
gen (A/F) sensor
connector.
Go to step 7. Go to step 6.
Go to step 8.
Repair the short Repair the poor
circuit to power in contact of ECM
the harness connector.
between ECM and
front oxygen (A/F)
sensor connector.
After repair,
replace the ECM.
<Ref. to
FU(H4SO)-45,
Engine Control
Module (ECM).>
Repair the exhaust Go to step 9.
system.