Subaru Legacy 2002 Service Manual page 1310

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
No.
1 CHECK GROUND CIRCUIT OF ECM.
1) Repair harness and connector.
NOTE:
In this case, repair the following:
¼ Open circuit in harness between ECM and
engine ground terminal
¼ Poor contact in ECM connector
¼ Poor contact in coupling connector (B22)
2) Measure resistance of harness between
ECM connector and chassis ground.
Connector & terminal
(B137) No. 31 — Chassis ground:
(B137) No. 21 — Chassis ground:
(B137) No. 8 — Chassis ground:
(B137) No. 9 — Chassis ground:
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.
NOTE:
¼ Subaru Select Monitor
For detailed operation procedure, refer to the
"READ CURRENT DATA FOR ENGINE".
<Ref. to EN(H6)-38, Subaru Select Monitor.>
¼ 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. 13 (+) — Chassis ground
(−):
4 CHECK OUTPUT SIGNAL FROM ECM.
Measure voltage between ECM connector
and chassis ground.
Connector & terminal
(B136) No. 13 (+) — Chassis ground
(−):
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. 13 (+) — Chassis ground
(−):
Step
Is the resistance less than
5 Ω?
Is the value more than 0.2
A?
Is the voltage less than 1.0
V?
Does the voltage change
less than 1.0 V by shaking
harness and connector of
ECM while monitoring the
value with voltage meter?
Is the voltage less than 1.0
V?
EN(H6)-103
Check Yes
Go to step 2.
Repair connector.
NOTE:
In this case,
repair the follow-
ing:
¼ Poor contact in
rear oxygen sen-
sor connector
¼ Poor contact in
rear oxygen sen-
sor connecting
harness connector
¼ Poor contact in
ECM connector
Go to step 6.
Repair poor con-
tact in ECM con-
nector.
Contact with your
Subaru distributor
service.
Engine (DIAGNOSTICS)
No
Repair harness
and connector.
NOTE:
In this case,
repair the follow-
ing:
¼ Open circuit in
harness between
ECM and engine
ground terminal
¼ Poor contact in
ECM connector
¼ Poor contact in
coupling connec-
tor
Go to step 3.
Go to step 4.
Go to step 5.
Repair battery
short circuit in
harness between
ECM and rear
oxygen sensor
connector.