EN(H4DOTC)(diag)-149
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AH:DTC P0171 SYSTEM TOO LEAN (BANK 1)
Refer to DTC P0172 for diagnostic procedure. <Ref. to EN(H4DOTC)(diag)-150, DTC P0172 SYSTEM TOO
RICH (BANK 1), Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
5
CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR.
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 connector and chassis ground.
Connector & terminal
(T6) No. 3 (+) — Chassis ground (–):
Is the voltage 0.2 — 0.5 V?
Replace the rear
oxygen sensor.
<Ref. to
FU(H4DOTC)-48,
Rear Oxygen Sen-
sor.>
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
• Open circuit of
harness between
the ECM and rear
oxygen sensor
• Poor contact of
the rear oxygen
sensor connector
• Poor contact in
ECM connector
6
CHECK EXHAUST SYSTEM.
Check exhaust system parts.
NOTE:
Check the following items.
• Looseness and improper attachment of ex-
haust system parts
• Damage (crack, hole etc.) of parts
• Looseness and improper attachment of parts
between front oxygen (A/F) sensor and rear ox-
ygen sensor
Is there any fault in exhaust
system?
Repair or replace
faulty parts.
Replace the rear
oxygen sensor.
<Ref. to
FU(H4DOTC)-48,
Rear Oxygen Sen-
sor.>
Step
Check
Yes
No