Subaru Impreza 2003 Service Manual page 545

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
1 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1)Turn the ignition switch to OFF.
2)Disconnect the connectors from ECM and
front oxygen (A/F) sensor connector.
3)Measure the resistance of harness between
ECM and front oxygen (A/F) sensor connector.
Connector & terminal
(B136) No. 13 — (B18) No. 1:
(B136) No. 22 — (B18) No. 2:
2 CHECK POOR CONTACT.
Check poor contact in front oxygen (A/F) sen-
sor connector.
Check
Is the resistance less than 1
Ω?
Is there poor contact in front
oxygen (A/F) sensor connec-
tor?
EN(H4SO)-133
ENGINE (DIAGNOSTICS)
Yes
Go to step 2. Repair harness
and connector.
NOTE:
In this case, repair
the following:
• Open circuit in
harness between
ECM and front
oxygen (A/F) sen-
sor connector
• Poor contact in
front oxygen (A/F)
sensor connector
• Poor contact in
ECM connector
Repair poor con- Replace the front
tact in front oxygen oxygen (A/F) sen-
(A/F) sensor con- sor. <Ref. to
nector. FU(H4SO)-44,
Front Oxygen (A/
F) Sensor.>
No