Subaru LEGACY 2006 Manual page 120

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Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
2 CHECK POWER SUPPLY TO FRONT OXY-
GEN (A/F) SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from front oxygen
(A/F) sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between front oxygen
(A/F) sensor connector and engine ground.
Connector & terminal
(E22) No. 6 (+) — Engine ground (–):
3 CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of front oxygen (A/F) 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(H4SO)(diag)-26, Subaru Select Monitor.>
• General scan tool
For detailed operation procedure, refer to the
general scan tool operation manual.
4 CHECK INPUT SIGNAL OF ECM.
1) Start and idle the engine.
2) Measure the voltage between ECM con-
nector and chassis ground.
Connector & terminal
(B136) No. 3 (+) — Chassis ground (–):
(B136) No. 2 (+) — Chassis ground (–):
5 CHECK OUTPUT SIGNAL OF ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B136) No. 3 (+) — Chassis ground (–):
(B136) No. 2 (+) — Chassis ground (–):
6 CHECK FRONT OXYGEN (A/F) SENSOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance between front oxy-
gen (A/F) sensor connector terminals.
Terminals
No. 4 — No. 6:
Check
Is the voltage more than 10 V? Go to step 3.
Is the current more than 0.2 A? Repair the poor
Is the voltage less than 1 V?
Does the voltage change by
shaking the ECM harness and
connector?
Is the resistance less than 10
Ω?
EN(H4SO)(diag)-83
ENGINE (DIAGNOSTICS)
Yes No
Repair the power
supply line or
replace the main
relay.
NOTE:
In this case, repair
the following item:
• Open circuit in har-
ness between oxy-
gen sensor relay and
front oxygen (A/F)
sensor connector
• Poor contact in
oxygen sensor relay
connector
• Poor contact in
coupling connector
Go to step 4.
contact of connec-
tor.
NOTE:
In this case, repair
the following item:
• Poor contact in
front oxygen (A/F)
sensor connector
• Poor contact in
ECM connector
Go to step 6. Go to step 5.
Repair the poor Go to step 6.
contact of ECM
connector.
Repair the har- Replace the front
ness and connec- oxygen (A/F) sen-
tor. sor. <Ref. to
FU(H4SO)-32,
NOTE:
Front Oxygen (A/F)
In this case, repair
Sensor.>
the following item:
• Open or ground
short circuit of har-
ness between front
oxygen (A/F) sen-
sor and ECM con-
nector
• Poor contact in
front oxygen (A/F)
sensor connector
• Poor contact in
ECM connector