Front Oxygen (A/F) Sensor - Subaru Legacy 2004 Service Manual

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
1 CHECK GROUND CIRCUIT FOR ECM.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B134) No. 6 — Chassis ground:
(B136) No. 7 — Chassis ground:
2 CHECK VOLTAGE BETWEEN ECM AND

FRONT OXYGEN (A/F) SENSOR.

Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B137) No. 2 (+) — Chassis ground (
(B137) No. 3 (+) — Chassis ground (
Check
Is the resistance less than 5
'?
Is the voltage more than 10 V? Repair the battery
"
):
"
):
EN(H4DOTC)(diag)-63
ENGINE (DIAGNOSTICS)
Yes
Go to step 2. Repair the open
circuit in harness
between ECM
connector and
chassis ground.
Repair the poor
short circuit in har- contact in ECM
ness between connector.
ECM and front
oxygen (A/F) sen-
sor connector.
No