Subaru Legacy 2003 Service Manual page 496

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
1 CHECK GROUND CIRCUIT OF ECM.
1) Turn ignition switch to OFF.
2) Disconnect connector from ECM.
3) Measure resistance of harness between
ECM connector and chassis ground.
Connector & terminal
(B136) No. 5 — Chassis ground:
(B136) No. 16 — Chassis ground:
Is the measured value less than the speci-
fied value?
2 CHECK CURRENT DATA.
1) Start engine.
2) Read data of rear oxygen sensor heater
current using Subaru Select Monitor or
OBD-II general scan tool.
Does the measured value exceed the spec-
ified value?
NOTE:
•Subaru Select Monitor
For detailed operation procedure, refer to the
"READ CURRENT DATA FOR ENGINE".
<Ref. to EN(H4SO)-32, Subaru Select Moni-
tor.>
•OBD-II scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Instruction Manual.
3 CHECK OUTPUT SIGNAL FROM ECM.
1) Start and idle the engine.
2) Measure voltage between ECM connector
and chassis ground.
Connector & terminal
(B136) No. 4 (+) — Chassis ground ( − − − − ):
Is the measured value less than the speci-
fied value?
4 CHECK OUTPUT SIGNAL FROM ECM.
Measure voltage between ECM connector and
chassis ground.
Connector & terminal
(B136) No. 4 (+) — Chassis ground ( − − − − ):
Is the measured value less than the specified
value by shaking harness and connector of
ECM while monitoring the value?
5 CHECK OUTPUT SIGNAL FROM ECM.
1) Disconnect connector from rear oxygen
sensor.
2) Measure voltage between ECM connector
and chassis ground.
Connector & terminal
(B136) No. 4 (+) — 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(H4SO)-99
ENGINE (DIAGNOSTICS)
Yes
Go to step 3. Go to step 2.
Repair connector. Go to step 3.
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 poor con- Go to step 5.
tact in ECM con-
nector.
Contact SUBARU Repair battery
distributor service. short circuit in har-
ness between
NOTE:
ECM and rear oxy-
Inspection by DTM
gen sensor con-
is required, be-
nector. After
cause probable
repair, replace
cause is deteriora-
ECM. <Ref. to
tion of multiple
FU(H4SO)-45,
parts.
Engine Control
Module.>
No