Subaru Legacy 2005 Service Manual page 1794

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step
1 CHECK POWER SUPPLY TO REAR OXY-
GEN SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from rear oxygen
sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between rear oxygen
sensor connector and chassis ground.
Connector & terminal
(E25) No. 2 (+) — Chassis ground (
2 CHECK GROUND CIRCUIT FOR ECM.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness
between ECM connector and chassis ground.
Connector & terminal
(B134) No. 4 — Chassis ground:
(B134) No. 5 — Chassis ground:
(B134) No. 6 — Chassis ground:
(B134) No. 7 — Chassis ground:
3 CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of rear oxygen sensor heater
current using Subaru Select Monitor or general
scan tool.
NOTE:
• Subaru Select Monitor
For detailed operation procedure, refer to
"READ CURRENT DATA FOR ENGINE". <Ref.
to EN(H6DO)(diag)-26, Subaru Select Moni-
tor.>
• General scan tool
For detailed operation procedure, refer to the
general scan tool operation manual.
4 CHECK OUTPUT SIGNAL FROM ECM.
1) Start and idle the engine.
2) Measure the voltage between ECM con-
nector and chassis ground.
Connector & terminal
(B135) No. 3 (+) — Chassis ground (
5 CHECK OUTPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B135) No. 3 (+) — Chassis ground (
Check
Is the voltage more than 10 V? Go to step 2.
−
):
Is the resistance less than 5
Ω?
Is the current more than 0.2 A? Repair the con-
Is the voltage less than 1 V?
−
):
Does the voltage change by
shaking the ECM harness and
connector while monitoring the
value of voltage meter?
−
):
EN(H6DO)(diag)-98
Yes
Repair the power
supply line.
NOTE:
In this case, repair
the following:
• Open circuit of
harness between
main relay and
rear oxygen sen-
sor connector
• Poor contact in
rear oxygen sen-
sor connector
• Poor contact in
coupling connector
Go to step 3. Repair the har-
ness and connec-
tor.
NOTE:
In this case, repair
the following:
• Open circuit of
harness between
ECM and engine
ground terminal
• Poor contact in
ECM connector
• Poor contact in
coupling connector
Go to step 4.
nector.
NOTE:
In this case, repair
the following:
• Poor contact in
rear oxygen sen-
sor connector
• Poor contact in
coupling connector
• Poor contact in
ECM connector
Go to step 7. Go to step 5.
Repair the poor Go to step 6.
contact in ECM
connector.
No