Subaru Legacy 2004 Service Manual page 511

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
(B135) No. 5 — Chassis ground:
(B135) No. 6 — Chassis ground:
2 CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of rear oxygen sensor heater
current using Subaru Select Monitor.
NOTE:
For detailed operation procedure, refer to
"READ CURRENT DATA FOR ENGINE". <Ref.
to EN(H4SO 2.0)(diag)-25, Subaru Select Mon-
itor.>
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
(B134) No. 1 (+) — Chassis ground (
4 CHECK OUTPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B134) No. 1 (+) — Chassis ground (
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
(B134) No. 1 (+) — Chassis ground (
Check
Is the resistance less than 5
&?
Is the current more than 0.2 A? Repair the con-
Is the voltage less than 1 V?
"
):
Does the voltage change by
shaking the ECM harness and
connector while monitoring the
value of voltage meter?
"
):
Is the voltage less than 1 V?
"
):
EN(H4SO 2.0)(diag)-79
ENGINE (DIAGNOSTICS)
Yes
Go to step 2. Repair the har-
ness and connec-
tor.
NOTE:
In this case, repair
the following:
• Open circuit in
harness between
ECM and engine
ground terminal
• Poor contact in
ECM connector
• Poor contact in
coupling connector
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 FU(H4SO short circuit in har-
2.0)-34, Engine ness between
Control Module ECM and rear oxy-
(ECM).> gen sensor con-
nector. After
repair, replace the
ECM. <Ref. to
FU(H4SO 2.0)-34,
Engine Control
Module (ECM).>
No