Subaru Legacy 2004 Service Manual page 611

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
1 CHECK ANY OTHER DTC ON DISPLAY.
2 CHECK FRONT OXYGEN (A/F) 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 (160!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 during idling using Subaru Select Moni-
tor or OBD-II general scan tool.
NOTE:
• Subaru Select Monitor
For detailed operation procedure, refer to
"READ CURRENT DATA FOR ENGINE". <Ref.
to EN(H4SO 2.0)(diag)-25, Subaru Select
Monitor.>
• OBD-II general scan tool
For detailed operation procedures, refer to
OBD-II General Scan Tool Instruction Manual.
3 CHECK FRONT OXYGEN (A/F) SENSOR DA-
TA.
Race the engine at speeds from idling to 5,000
rpm for a total of 5 cycles.
NOTE:
• Air fuel ratio is rich at normal condition or
during racing.
• 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 the ignition switch to OFF.
2) Disconnect the connector from ECM and
front oxygen (A/F) sensor connector.
3) Measure the resistance between ECM and
front oxygen (A/F) sensor.
Connector & terminals
(B136) No. 33 — (E24) No. 1:
(B136) No. 35 — (E24) No. 2:
5 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR.
Measure the resistance between ECM and
chassis ground.
Connector & terminals
(B136) No. 33 — Chassis ground:
(B136) No. 35 — Chassis ground:
Check
Is any other DTC displayed?
Is the voltage 0.85 — 1.15 V? Go to step 3.
Is the voltage more than 1.1 V? Go to step 6.
Is the resistance less than 5
&?
Is the resistance more than 1
M&?
EN(H4SO 2.0)(diag)-179
ENGINE (DIAGNOSTICS)
Yes
Inspect DTC using Go to step 2.
"List of Diagnostic
Trouble Code
(DTC)". <Ref. to
EN(H4SO
2.0)(diag)-66, List
of Diagnostic Trou-
ble Code (DTC).>
Go to step 4.
Go to step 4.
Go to step 5. Repair the open
circuit between
ECM and front
oxygen (A/F) sen-
sor.
Go to step 6. Repair the ground
short circuit
between ECM and
front oxygen (A/F)
sensor.
No