Mazda 6 2002 Workshop Manual page 214

DTC P0171 Fuel trim system too lean
• Misfire
• Front HO2S deterioration
• Front HO2S heater malfunction
• Pressure regulator malfunction
• Fuel pump malfunction
• Fuel filter clogged or restricted
POSSIBLE
• Fuel leakage on fuel line from fuel delivery pipe and fuel pump
CAUSE
• Fuel return hose clogged
• Leakage ehaust system
• Purge solenoid valve malfunction
• Purge solenoid hoses improper connection
• Insufficient compression
• Variable valve timing control system improper operation (L3-VE)
Diagnostic procedure
STEP
1 PERFORM DTC CONFIRMATION PROCEDURE
• Perform DTC CONFIRMATION PROCEDURE.
(See F–66 DTC CONFIRMATION
PROCEDURE.)
• Is same DTC present?
2 VERIFY RELATED PENDING CODE OR
STORED DTCS
• Turn ignition key to OFF, then ON (Engine
OFF).
• Verify related PENDING CODE or stored
DTCs.
• Is other DTCs present?
3 IDENTIFY TRIGGER DTC FOR FREEZE FRAME
DATA
• Is DTC P0171 on FREEZE FRAME DATA?
4 VERIFY CURRENT INPUT SIGNAL STATUS
(IGNITION KEY TO ON/IDLE)
• Access ECT, MAF, TP and VSS PIDs using
WDS or equivalent.
(See F–45 PCM
• Is there any signal that is far out of
specification when ignition key is ON and
engine runs?
5 VERIFY CURRENT INPUT SIGNAL STATUS
UNDER TROUBLE CONDITION
• Inspect same PIDs as Step 4 while simulating
FREEZE FRAME DATA condition.
• Is there any input signal which causes drastic
changes?
6 VERIFY CURRENT INPUT SIGNAL STATUS OF
FRONT HO2S
• Access O2S11 for P0171 PID using WDS or
equivalent.
• Check PID under following accelerator pedal
condition (in PARK (ATX) or NEUTRAL
(MTX)).
• Is PID reading okay?
— Above 0.55 V when accelerator pedal is
suddenly depressed (rich condition).
— Below 0.55 V just after release of
accelerator pedal (lean condition)
ON-BOARD DIAGNOSTIC
INSPECTION
INSPECTION.)
Yes Go to net step.
No Intermittent concern eists. Go to INTERMITTENT
CONCERN TROUBLESHOOTING procedure.
(See F–227 INTERMITTENT CONCERN
TROUBLESHOOTING.)
Yes If misfire DTC is present, go to step 7.
If other DTC is present, go to appropriate DTC
troubleshooting procedures.
(See F–67 DTC TABLE.)
No If drive ability concern is present, go to Step 7.
If not, go to net step.
Yes Go to net step.
No Go to troubleshooting procedures for DTC on FREEZE
FRAME DATA.
Yes Inspect suspected sensor and ecessive resistance in
related wiring harnesses. Repair or replace if necessary.
Then go to Step 18.
No Go to net step.
Yes Inspect suspected sensor and related wiring harnesses,
and repair or replace it. Then go to Step 18.
No Go to net step.
Yes Inspect for air suction at followings due to cracks, damages
and loosening parts:
• From air cleaner to throttle body
• From throttle body to dynamic chamber
• From dynamic chamber to intake manifold
• Vacuum hoses
Note
• Engine speed may change when rust penetrating
agent is sprayed on the air suction area.
Repair or replace any faulty part, then go to Step 18.
No Visually inspect for any gas leakage between ehaust
manifold and front HO2S.
• If there is no leakage, replace FRONT HO2S.
Then go to Step 18.
ACTION
F–117
F