Subaru Legacy 2004 Service Manual page 507

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
7 CHECK FRONT OXYGEN (A/F) SENSOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance between front oxy-
gen (A/F) sensor connector terminals.
Terminals
No. 3 — No. 4:
Check
Is the resistance less than 10
&?
EN(H4SO 2.0)(diag)-75
ENGINE (DIAGNOSTICS)
Yes
Repair the har- Replace the front
ness and connec- oxygen (A/F) sen-
tor. sor. <Ref. to
FU(H4SO 2.0)-32,
NOTE:
Front Oxygen (A/
In this case, repair
F) Sensor.>
the following:
• Open or ground
short circuit in har-
ness between front
oxygen (A/F) sen-
sor and ECM con-
nector
• Poor contact in
front oxygen (A/F)
sensor connector
• Poor contact in
ECM connector
No