Subaru Legacy 2003 Service Manual page 1910

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
1 CHECK OUTPUT SIGNAL FROM ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM con-
nector and chassis ground.
Connector & terminal
(B137) No. 4 (+) — Chassis ground ( − − − − ):
(B137) No. 5 (+) — Chassis ground ( − − − − ):
Does the measured value exceed the spec-
ified value?
2 CHECK FRONT OXYGEN (A/F) SENSOR
HEATER CURRENT.
1) Turn the ignition switch to OFF.
2) Repair the battery short circuit in harness
between ECM and front oxygen (A/F) sen-
sor connector.
3) Turn the ignition switch to ON.
4) Read the data of front oxygen (A/F) sensor
heater current using Subaru Select Monitor.
Does the measured value exceed the spec-
ified value?
NOTE:
For detailed operation procedure, refer to the
"READ CURRENT DATA FOR ENGINE". <Ref.
to EN(H4DOSTC)-26, Subaru Select Monitor.>
3 CHECK OUTPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B137) No. 4 (+) — Chassis ground ( − − − − ):
(B137) No. 5 (+) — Chassis ground ( − − − − ):
Does the measured value exceed the specified
value by shaking harness and connector of
ECM while monitoring the value with voltage
meter?
Value
8 V
2.3 A
8.0 V
EN(H4DOSTC)-71
ENGINE (DIAGNOSTICS)
Yes
Go to step 3. Go to step 2.
Replace the ECM. END
<Ref. to
FU(H4DOSTC)-
40, Engine Con-
trol Module.>
Repair the battery END
short circuit in har-
ness between
ECM and front
oxygen (A/F) sen-
sor connector.
No