Subaru Impreza 2004 Service Manual page 203

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
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
(B84) No. 29 — (B18) No. 3:
(B84) No. 19 — (B18) No. 4:
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(H4DOTC)(diag)-282
Yes
Go to step 2. Repair the har-
ness and connec-
tor.
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 the poor Replace the front
contact in front oxygen (A/F) sen-
oxygen (A/F) sen- sor. <Ref. to
sor connector. FU(H4DOTC)-44,
Front Oxygen (A/
F) Sensor.>
No