Subaru Impreza 2004 Service Manual page 62

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
5 CHECK HARNESS BETWEEN REAR OXY-
GEN SENSOR AND ECM CONNECTOR.
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 harness connector and engine ground
or chassis ground.
Connector & terminal
LHD model
(B19) No. 3 (+) — Engine ground ( − − − − ):
RHD model
(B19) No. 4 (+) — Engine ground ( − − − − ):
6 CHECK EXHAUST SYSTEM.
Check the exhaust system parts.
NOTE:
Check the following items.
•Loose installation of portions
•Damage (crack, hole etc.) of parts
•Looseness and ill fitting of parts between front
oxygen (A/F) sensor and rear oxygen sensor
Check
Is the voltage more than 0.2 V? Replace the rear
Is there a fault in exhaust sys-
tem?
EN(H4DOTC)(diag)-141
ENGINE (DIAGNOSTICS)
Yes
Repair the har-
oxygen sensor. ness and connec-
<Ref. to tor.
FU(H4DOTC)-46,
NOTE:
Rear Oxygen Sen-
In this case, repair
sor.>
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
Repair or replace Replace the rear
the faulty parts. oxygen sensor.
<Ref. to
FU(H4DOTC)-46,
Rear Oxygen Sen-
sor.>
No