Subaru 2002 IMPREZA Service Manual page 1301

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
1 CHECK ANY OTHER DIAGNOSTIC TROU-
BLE CODE (DTC) ON DISPLAY.
2 CHECK FRONT (A/F) OXYGEN SENSOR DA-
TA.
1)Start the engine.
2)While observing the Subaru Select Monitor
or OBD-II general scan tool screen, warm-up
the engine until coolant temperature is above
70°C (158°F).
If the engine is already warmed-up, operate at
idle speed for at least 1 minute.
3)Read the data of front oxygen (A/F) sensor
signal using Subaru Select Monitor or OBD-II
general scan tool.
NOTE:
•Subaru Select Monitor
For detailed operation procedure, refer to the
"READ CURRENT DATA FOR ENGINE".
<Ref. to EN(TURBO)-34, Subaru Select Moni-
tor.>
•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 the engine at speeds from idling to
5,000 rpm for a total of 5 cycles.
NOTE:
To increase the engine speed to 5,000 rpm,
slowly depress accelerator pedal, taking ap-
prox. 5 seconds, and quickly release accelera-
tor pedal to decrease engine speed.
2)Operate the LED operation mode for engine.
NOTE:
•Subaru Select Monitor
For detailed operation procedure, refer to the
"LED OPERATION MODE FOR ENGINE".
<Ref. to EN(TURBO)-34, Subaru Select Moni-
tor.>
4 CHECK EXHAUST SYSTEM.
Check the exhaust system parts.
NOTE:
Check the following items.
•Loose installation of portions
•Damage (crack, hole etc.) of parts
•Looseness of front oxygen (A/F) sensor
•Looseness and ill fitting of parts between front
oxygen (A/F) sensor and rear oxygen sensor
Check
Is any other DTC displayed?
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 sys-
tem?
EN(TURBO)-141
ENGINE (DIAGNOSTICS)
Yes
Inspect the rele- Go to step 2.
vant DTC using
"List of Diagnostic
Trouble Code
(DTC)".<Ref. to
EN(TURBO)-75,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 3. Go to step 4.
Repair the poor Check the rear
contact in front oxygen sensor cir-
oxygen (A/F) sen- cuit. <Ref. to
sor and rear oxy- FU(TURBO)-46,
gen sensor Rear Oxygen Sen-
connector. sor.>
Repair or replace Replace the front
the faulty parts. oxygen (A/F) sen-
sor. <Ref. to
FU(TURBO)-44,
Front Oxygen (A/
F) Sensor.>
No