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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 or the SHRTFT 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 the PCM detects the above malfunction 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 the PCM detects the above malfunction condition 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 No.1 signal malfunction
MAF sensor signal malfunction
TP sensor signal malfunction
VSS signal malfunction
Related connector or terminals malfunction
Related wiring harness malfunction
A/F sensor heater malfunction
A/F sensor malfunction
A/F sensor looseness
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