Subaru Legacy 2002 Service Manual page 1527

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Engine (DIAGNOSTICS)
No.
1 CHECK ANY OTHER DTC ON DISPLAY.
2 CHECK FRONT (A/F) OXYGEN SENSOR
DATA.
1) Start engine.
2) While observing the Subaru Select Monitor
or OBD-II general scan tool screen, warm-up
the engine until coolant temperature is above
75°C (167°F).
If the engine is already warmed-up, operate at
idle speed for at least 1 minute.
3) Read data of front oxygen (A/F) sensor
signal using Subaru Select Monitor or OBD-II
general scan tool.
NOTE:
¼ Subaru Select Monitor
For detailed operation procedure, refer to the
"READ CURRENT DATA FOR ENGINE".
<Ref. to EN(H6)-38, Subaru Select Monitor.>
¼ OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Instruction Manual.
3 CHECK REAR OXYGEN SENSOR SIGNAL.
1) Race engine at speeds from idling to 5,000
rpm for a total of 5 cycles.
NOTE:
To increase engine speed to 5,000 rpm,
slowly depress accelerator pedal, taking
approximately 5 seconds, and quickly release
accelerator pedal to decrease engine speed.
2) Operate the LED operation mode for
engine.
NOTE:
¼ Subaru Select Monitor
For detailed operation procedure, refer to the
"LED OPERATION MODE FOR ENGINE".
<Ref. to EN(H6)-38, Subaru Select Monitor.>
4 CHECK EXHAUST SYSTEM.
Check exhaust system parts.
NOTE:
Check the following items.
¼ Loose installation of portions
¼ Damage (crack, hole etc.) of parts
¼ Looseness of front oxygen (A/F) sensor
¼ Looseness and ill fitting of parts between
front oxygen (A/F) sensor and rear oxygen
sensor
Step
Is there any other DTC on
display?
Is the value equal to or
more than 0.85 and equal
to less than 1.15 in idling?
Does the LED of {Rear O2
Rich Signal} blink?
Is there a fault in exhaust
system?
EN(H6)-320
Check Yes
Inspect the rel-
evant DTC using
"List of Diagnostic
Trouble Code
(DTC)". <Ref. to
EN(H6)-87, List of
Diagnostic
Trouble Code
(DTC).>
Go to step 3.
Repair poor con-
tact in front oxy-
gen (A/F) sensor
and rear oxygen
sensor connector.
Repair or replace
faulty parts.
No
Go to step 2.
Go to step 4.
Check rear oxy-
gen sensor circuit.
<Ref. to FU(H6)-
46, Rear Oxygen
Sensor.>
Replace front oxy-
gen (A/F) sensor.
<Ref. to FU(H6)-
43, Front Oxygen
(A/F) Sensor.>