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 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 check engine light 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.
FAIL-SAFE FUNCTION	-
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 Related connector or terminals malfunction Related wiring harness 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 Fuel supply system malfunction Pressure regulator malfunction (built-into fuel pump unit) Fuel pump unit malfunction Fuel leakage in fuel line between fuel distributor and fuel pump Fuel filter restricted (built-into fuel pump unit) Fuel return hose restricted Ignition system malfunction Ignition coil related wiring harness malfunction Spark plug malfunction Ignition coil malfunction Insufficient engine compression Improper operation of fuel injector PCM malfunction
SYSTEM WIRING DIAGRAM	-