Subaru Legacy 2005 Service Manual page 1350

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
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 chassis ground.
Connector & terminal
(T6) No. 4 (+) — Chassis ground (
6 CHECK EXHAUST SYSTEM.
Check exhaust system parts.
NOTE:
Check the following items.
• Loose part and incomplete installation of
exhaust system
• Damage (crack, hole etc.) of parts
• Looseness and ill fitting of parts between
front oxygen (A/F) sensor and rear oxygen
sensor
T: DTC P0171 SYSTEM TOO LEAN (BANK 1)
NOTE:
For the diagnostic procedure, refer to DTC P0172. <Ref. to EN(H4DOTC)(diag)-111, DTC P0172 SYSTEM
TOO RICH (BANK 1), Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
Check
Is the voltage more than 0.2 V? Replace the rear
−
):
Is there any fault in exhaust
system?
EN(H4DOTC)(diag)-110
Yes
Repair the har-
oxygen sensor. ness and connec-
<Ref. to tor.
FU(H4DOTC)-33,
NOTE:
Rear Oxygen Sen-
In this case, repair
sor.>
the following:
• Open circuit of
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
faulty parts. oxygen sensor.
<Ref. to
FU(H4DOTC)-33,
Rear Oxygen Sen-
sor.>
No