Subaru 2009 IMPREZA Service Manual page 698

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
16 CHECK REAR OXYGEN SENSOR CONNEC-
TOR AND COUPLING CONNECTOR.
17 CHECK FRONT OXYGEN (A/F) SENSOR
AND REAR OXYGEN SENSOR DATA.
1) Warm up the engine until engine coolant
temperature is higher than 75°C (167°F), then
keep the engine idling for 5 minutes or more.
2) Read the data of rear oxygen sensor signal
using Subaru Select Monitor or general scan
tool.
NOTE:
• Subaru Select Monitor
For detailed operation procedures, refer to
"READ CURRENT DATA FOR ENGINE". <Ref.
to EN(H4SO)(diag)-34, Subaru Select Moni-
tor.>
• General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
18 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:
19 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between rear oxygen
sensor connector and chassis ground.
Connector & terminal
(E23) No. 3 (+) — Chassis ground (–):
Check
Has water entered the connec-
tor?
Is a voltage of 0.8 V or more
maintained for 5 minutes or
more?
Is the resistance less than 1 ? Go to step 19.
Is the voltage 0.2 — 0.5 V?
EN(H4SO)(diag)-281
ENGINE (DIAGNOSTICS)
Yes No
Completely Go to step 18.
remove any water
inside.
Replace the front Go to step 18.
oxygen (A/F) sen-
sor. <Ref. to
FU(H4SO)-41,
Front Oxygen (A/F)
Sensor.>
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
• Open circuit in
harness between
ECM and rear oxy-
gen sensor con-
nector
• Poor contact of
coupling connector
Replace the rear Repair the harness
oxygen sensor. and connector.
<Ref. to
NOTE:
FU(H4SO)-43,
In this case, repair
Rear Oxygen Sen-
the following item:
sor.>
• Open circuit in
harness between
ECM and rear oxy-
gen sensor con-
nector
• Poor contact of
ECM connector
• Poor contact of
coupling connector