Subaru 2009 IMPREZA Service Manual page 565

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step
1 CHECK FRONT OXYGEN (A/F) SENSOR
CONNECTOR AND COUPLING CONNEC-
TOR.
2 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from front oxy-
gen (A/F) sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between ECM and
chassis ground.
Connector & terminal
(B135) No. 9 (+) — Chassis ground (–):
(B135) No. 8 (+) — Chassis ground (–):
Check
Has water entered the connec-
tor?
Is the voltage 8 V or more?
EN(H4SO)(diag)-148
Yes No
Completely Go to step 2.
remove any water
inside.
Repair the short Replace the front
circuit to power in oxygen (A/F) sen-
the harness sor. <Ref. to
between ECM and FU(H4SO)-41,
front oxygen (A/F) Front Oxygen (A/F)
sensor connector. Sensor.>