Subaru Legacy 2003 Service Manual page 1912

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
1 CHECK GROUND CIRCUIT OF ECM.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness
between ECM connector and chassis
ground.
Connector & terminal
(B137) No. 8 — Chassis ground:
(B137) No. 9 — Chassis ground:
Is the measured value less than the speci-
fied value?
2 CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of rear oxygen 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.
1) Start and idle the engine.
2) Measure the voltage between ECM con-
nector and chassis ground.
Connector & terminal
(B136) No. 13 (+) — Chassis ground ( − − − − ):
Is the measured value less than the speci-
fied value?
4 CHECK OUTPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B136) No. 13 (+) — Chassis ground ( − − − − ):
Is the measured value less than the specified
value by shaking harness and connector of
ECM while monitoring the value with voltage
meter?
5 CHECK OUTPUT SIGNAL FROM ECM.
1) Disconnect the connector from rear oxygen
sensor.
2) Measure the voltage between ECM con-
nector and chassis ground.
Connector & terminal
(B136) No. 13 (+) — Chassis ground ( − − − − ):
Is the measured value less than the speci-
fied value?
Value
5 Ω
0.2 A
1.0 V
1.0 V
1.0 V
EN(H4DOSTC)-73
ENGINE (DIAGNOSTICS)
Yes
Go to step 3. Go to step 2.
Repair the con- Go to step 3.
nector.
NOTE:
In this case, repair
the following:
• Poor contact in
rear oxygen sen-
sor connector
• Poor contact in
rear oxygen sen-
sor connecting
harness connector
• Poor contact in
ECM connector
Go to step 6. Go to step 4.
Repair the poor Go to step 5.
contact in ECM
connector.
Replace the ECM. Repair the battery
<Ref. to short circuit in har-
FU(H4DOSTC)- ness between
40, Engine Con- ECM and rear oxy-
trol Module.> gen sensor con-
nector. After
repair, replace the
ECM. <Ref. to
FU(H4DOSTC)-
40, Engine Con-
trol Module.>
No