Subaru Legacy 2002 Service Manual page 656

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
No.
1 CHECK ANY OTHER DTC ON DISPLAY.
2 CHECK FRONT OXYGEN (A/F) 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
70°C (158°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-34, 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 FRONT OXYGEN (A/F) SENSOR
DATA.
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.
4 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR.
1) Turn ignition switch to OFF.
2) Disconnect connector from ECM and front
oxygen (A/F) sensor connector.
3) Measure resistance between ECM and
front oxygen (A/F) sensor.
Connector & terminals
(B136) No. 6 — (B18) No. 3:
(B136) No. 7 — (B18) No. 4:
(B136) No. 19 — (B18) No. 1:
(B136) No. 20 — (B18) No. 6:
Step
Does the Subaru Select
Monitor or OBD-II general
scan tool indicate DTC
P0131, P0132, P0031 or
P0032?
Is the value equal to or
more than 0.85 and equal
to less than 1.15 in idling?
Is the value more than 1.1
for a moment?
Is the resistance less than
5 Ω?
EN-139
Check Yes
Inspect DTC
P0131, P0132,
P0031 or P0032
using "17. List of
Diagnostic
Trouble Code
(DTC)". <Ref. to
EN-82, List of
Diagnostic
Trouble Code
(DTC).>
Go to step 3.
Go to step 6.
Go to step 5.
Engine (Diagnostics)
No
Go to step 2.
Go to step 4.
Go to step 4.
Repair open cir-
cuit between ECM
and front oxygen
(A/F) sensor.