Subaru Legacy 2003 Service Manual page 674

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
1 CHECK ANY OTHER DTC ON DISPLAY.
Is any other DTC displayed?
2 CHECK FRONT OXYGEN (A/F) SENSOR DA-
TA.
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 sig-
nal using Subaru Select Monitor or OBD-II
general scan tool.
Is the measured value within the specified
range?
NOTE:
•Subaru Select Monitor
For detailed operation procedure, refer to the
"READ CURRENT DATA FOR ENGINE".
<Ref. to EN(H4SO)-32, 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 FRONT OXYGEN (A/F) SENSOR DA-
TA.
Race engine at speeds from idling to 5,000
rpm for a total of 5 cycles.
Does the measured value exceed the specified
value?
NOTE:
•Normally, A/F mixture ratio is rich with racing
engine.
•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. 13 — (B18) No. 1:
(B136) No. 22 — (B18) No. 2:
Is the measured value less than the speci-
fied value?
Value
DTC indicated.
0.85 - 1.15
1.1
5 Ω
EN(H4SO)-277
ENGINE (DIAGNOSTICS)
Yes
Inspect the rele- Go to step 2.
vant DTC using
"List of Diagnostic
Trouble Code
(DTC)". <Ref. to
EN(H4SO)-83, List
of Diagnostic
Trouble Code
(DTC).>
Go to step 3. Go to step 4.
Go to step 6. Go to step 4.
Go to step 5. Repair open circuit
between ECM and
front oxygen (A/F)
sensor.
No