Subaru Legacy 2004 Service Manual page 848

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
6 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
(B135) No. 2 (+) — Chassis ground (
7 CHECK POWER SUPPLY TO REAR OXY-
GEN SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from rear oxygen
sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between rear oxygen
sensor connector and chassis ground.
Connector & terminal
(B19) No. 2 (+) — Chassis ground (
8 CHECK REAR OXYGEN SENSOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance between rear oxy-
gen (A/F) sensor connector terminals.
Terminals
No. 1 — No. 2:
Check
Is the voltage less than 1 V?
"
):
Is the voltage more than 10 V? Go to step 8.
"
):
Is the resistance less than 30
!?
EN(H4SO 2.5)(diag)-89
ENGINE (DIAGNOSTICS)
Yes
Replace the ECM. Repair the battery
<Ref. to FU(H4SO short circuit in har-
2.5)-36, Engine ness between
Control Module ECM and rear oxy-
(ECM).> gen sensor con-
nector. After
repair, replace the
ECM. <Ref. to
FU(H4SO 2.5)-36,
Engine Control
Module (ECM).>
Repair the power
supply line.
NOTE:
In this case, repair
the following:
• Open circuit in
harness between
main relay and
rear oxygen sen-
sor connector
• Poor contact in
rear oxygen sen-
sor connector
• Poor contact in
coupling connector
Repair the har- Replace the rear
ness and connec- oxygen sensor.
tor. <Ref. to FU(H4SO
2.5)-35, Rear Oxy-
NOTE:
gen Sensor.>
In this case, repair
the following:
• Open circuit in
harness between
rear oxygen sen-
sor and ECM con-
nector
• Poor contact in
rear oxygen sen-
sor connector
• Poor contact in
ECM connector
• Poor contact in
coupling connector
No