Subaru 2002 IMPREZA Service Manual page 584

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
ENGINE (DIAGNOSTICS)
Step
7 CHECK GROUND CIRCUIT OF ECM.
1)Repair the harness and connector.
2)Measure the resistance of harness between
ECM connector and chassis ground.
Connector & terminal
(B136) No. 22 — Chassis ground:
8 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
(B19) No. 4 (+) — Engine ground ( − − − − ):
9 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 resistance less than 5
Ω?
Is the voltage more than 0.2 V? Replace the rear
Is there a fault in exhaust sys-
tem?
EN-152
Yes
Go to step 8. Repair the har-
ness and connec-
tor.
NOTE:
In this case, repair
the following:
• Open circuit in
harness between
ECM and engine
ground terminal
• Poor contact in
ECM connector
• Poor contact in
coupling connector
(B22)
Repair the har-
oxygen sensor. ness and connec-
<Ref. to FU-47, tor.
Front Oxygen (A/
NOTE:
F) Sensor.>
In this case, repair
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-47,
Front Oxygen (A/
F) Sensor.>
No