Subaru IMPREZA GD 2007 Series Manual page 1468

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Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
1 CHECK REAR OXYGEN SENSOR DATA.
1) Warm-up the engine until engine coolant
temperature is higher than 75°C (167°F), and
keep the engine speed at 3,000 rpm. (2 minutes
maximum)
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(STI)(diag)-33, Subaru Select Monitor.>
• General scan tool
For detailed operation procedure, refer to the
general scan tool operation manual.
2 CHECK REAR OXYGEN SENSOR DATA.
1) Warm-up the engine until engine coolant
temperature is higher than 75°C (167°F), and
rapidly reduce the engine speed from 3,000 rpm.
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(STI)(diag)-33, Subaru Select Monitor.>
• General scan tool
For detailed operation procedure, refer to the
general scan tool operation manual.
3 CHECK REAR OXYGEN SENSOR CONNEC-
TOR AND COUPLING CONNECTOR.
4 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 — (T6) No. 3:
(B135) No. 30 — (T6) No. 4:
5 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN 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 chassis ground.
Connector & terminal
(T6) No. 3 (+) — Chassis ground (–):
Check
Is the voltage 490 mV or more? Go to step 6.
Is the voltage 250 mV or less? Go to step 6.
Has water entered the connec-
tor?
Is the resistance less than 1 Ω? Go to step 5.
Is the voltage 0.2 — 0.5 V?
EN(STI)(diag)-137
ENGINE (DIAGNOSTICS)
Yes No
Go to step 2.
Go to step 3.
Completely remove Go to step 4.
any water inside.
Repair the open
circuit of harness
between ECM and
rear oxygen sensor
connector.
Replace the rear Repair the harness
oxygen sensor. and connector.
<Ref. to
NOTE:
FU(H4DOTC)-48,
In this case, repair
Rear Oxygen Sen-
the following item:
sor.>
• Open circuit of
harness between
the ECM and rear
oxygen sensor
• Poor contact of
the rear oxygen
sensor connector
• Poor contact in
ECM connector