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DTC P0171-00; Fuel Trim System Too Lean: Notes

NOTE:

To determine the malfunctioning part, proceed with the diagnostics from "Function Inspection Using M-MDS".

Details On DTCs

DETECTION CONDITION AND POSSIBLE CAUSE

DESCRIPTION	Fuel trim system too lean
DETECTION CONDITION	Determination conditions	Any one of the following conditions is met: The sum of the fuel feedback correction amount (SHRTFT1) and the fuel learning correction amount (LONGFT1) is the specified value (30 %) or more, and 10 s or more have elapsed with the fuel learning correction amount (LONGFT1) at the specified value (15 %) or more. While the engine is idling or the vehicle is driven, the fuel feedback correction amount reaches the upper limit (25 % or more) for 20 s or more.
	Preconditions	Engine coolant temperature: 0-45 °C {32-113 °F}, 60 °C {140 °F} or more^1 ^1 : Value can be verified by displaying PIDs using M-MDS
	Malfunction determination period	10 s or 20 s period
	Drive cycle	2
	Self test type	CMDTC self test
	Sensor used	A/F sensor
FAIL-SAFE FUNCTION	Not applicable
VEHICLE STATUS WHEN DTCs ARE OUTPUT	Illuminates check engine light.
POSSIBLE CAUSE	Erratic signal to PCM ECT sensor No. 1 signal malfunction MAF sensor signal malfunction MAP sensor signal malfunction IAT sensor No. 2 signal malfunction Related connector or terminals malfunction Related wiring harness malfunction High-pressure side fuel delivery system malfunction High fuel pressure sensor malfunction Relief valve (built-into high pressure fuel pump) malfunction Spill valve control solenoid valve control circuit malfunction (damage to driver in PCM caused by short circuit to ground system) Spill valve control solenoid valve (built-into high pressure fuel pump) malfunction High pressure fuel pump malfunction Fuel leakage in fuel line Low-pressure side fuel delivery system malfunction Fuel filter clogged (built-into fuel pump unit) Low pressure side fuel line restriction (between fuel pump unit and high pressure fuel pump) Fuel pump unit malfunction Pressure regulator (built-into fuel pump unit) malfunction Fuel pump control module malfunction Fuel injector malfunction Improper operation of fuel injector Fuel injector related wiring harness malfunction Improper operation of purge control system Purge solenoid valve malfunction Purge solenoid hoses improper connection PCV valve malfunction MAF sensor malfunction Air cleaner element malfunction MAP sensor malfunction Air suction in intake air system Improper operation of electric variable valve timing control system Electric variable valve timing driver malfunction Electric variable valve timing motor malfunction Electric variable valve timing actuator malfunction Improper operation of hydraulic variable valve timing control system A/F sensor malfunction A/F sensor loose Exhaust system leakage Poor fuel quality PCM malfunction