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DTC P0171:00: Notes
DTC P0171:00
Fuel trim system too lean
DETECTION CONDITION
The PCM monitors short term fuel trim (SHRTFT) and long term fuel trim (LONGFT) values when closed loop fuel control. If the LONGFT and the sum total of these fuel trims exceed preprogrammed criteria, the PCM determines that the fuel system is too lean.
Diagnostic support note
This is a continuous monitor (fuel system).
The MIL illuminates if PCM detects the above malfunctioning condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM.
PENDING CODE is available if PCM detects the above malfunction conditions during first drive cycle.
FREEZE FRAME DATA (Mode 2)/Snapshot data is available.
The DTC is stored in the PCM memory.
POSSIBLE CAUSE
Misfire
Erratic signal to PCM
APP sensor signal malfunction
ECT sensor signal malfunction
MAF sensor signal malfunction
TP sensor signal malfunction
VSS signal malfunction
A/F sensor heater malfunction
A/F sensor malfunction
A/F sensor loose
Exhaust system leakage
A/F sensor deterioration
Air suction in intake air system
MAF sensor malfunction
Improper operation of purge control system
Improper operation of variable valve timing control system
Fuel supply system malfunction
Pressure regulator malfunction
Fuel pump malfunction
Fuel leakage on fuel line from fuel distributor and fuel pump