Subaru Legacy 2003 Service Manual page 554

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
1 CHECK ANY OTHER DTC ON DISPLAY.
Does the Subaru Select Monitor or OBD-II
general scan tool indicate DTC P0130, P0131,
P0132 or P0134?
2 CHECK REAR OXYGEN SENSOR DATA.
1) Warm-up the engine until engine coolant
temperature is above 70°C (158°F), and
race engine until the engine speed reaches
to 5,000 rpm and release accelerator pedal
rapidly.
2) Read data of rear oxygen sensor signal
using Subaru Select Monitor or OBD-II gen-
eral scan tool.
Does the value fluctuate?
NOTE:
•Subaru Select Monitor
For detailed operation procedure, refer to the
"READ CURRENT DATA SHOWN ON DIS-
PLAY FOR ENGINE". <Ref. to EN(H4SO)-32,
Subaru Select Monitor.>
•OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Instruction Manual.
3 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn ignition switch to OFF.
2) Disconnect connectors from ECM and rear
oxygen sensor.
3) Measure resistance of harness between
ECM and rear oxygen sensor connector.
Connector & terminal
(B135) No. 14 — (T6) No. 4:
(B135) No. 19 — (T6) No. 3:
Does the measured value exceed the spec-
ified value?
4 CHECK HARNESS BETWEEN REAR OXY-
GEN SENSOR AND ECM CONNECTOR.
1) Turn ignition switch to OFF.
2) Disconnect connector from rear oxygen
sensor.
3) Turn ignition switch to ON.
4) Measure voltage between rear oxygen sen-
sor harness connector and engine ground
or chassis ground.
Connector & terminal
(T6) No. 4 (+) — Engine ground ( − − − − ):
Is the measured value within the specified
range?
Value
DTC indicated.
250 mV
3 Ω
0.2 V - 0.5 V
EN(H4SO)-157
ENGINE (DIAGNOSTICS)
Yes
Check DTC refer- Go to step 3.
ring "List of Diag-
nostic Trouble
Code (DTC)".
<Ref. to
EN(H4SO)-83, List
of Diagnostic
Trouble Code
(DTC).>
NOTE:
In this case,
CHECKING proce-
dure for P0138 is
not necessary.
Go to step 5. Go to step 3.
Repair open circuit Go to step 4.
in harness
between ECM and
rear oxygen sen-
sor connector.
Replace rear oxy- Repair harness
gen sensor. <Ref. and connector.
to FU(H4SO)-43,
NOTE:
Rear Oxygen Sen-
In this case, repair
sor.>
the following:
• Open circuit in
harness between
rear oxygen sen-
sor and ECM con-
nector
• Poor contact in
rear oxygen sen-
sor connector
• Poor contact in
ECM connector
No