DTC P0171 [LF]: Notes
DTC P0171 (LF) DETECTION CONDITION AND POSSIBLE CAUSE
| DTC P0171 |
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 PCM detects above malfunction condition in two consecutive drive cycles or in one drive cycle while DTC for the same malfunction has been stored in PCM.
- PENDING CODE is available if PCM detects the above malfunction condition during first drive cycle.
- FREEZE FRAME DATA (Mode 2/Mode 12) is available.
- The DTC is stored in the PCM memory.
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| POSSIBLE CAUSE |
- 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 looseness
- Leakage exhaust system
- A/F sensor deterioration
- Air suction in intake air system
- MAF sensor malfunction
- Improper operation of purge solenoid valve
- Purge solenoid valve malfunction (stuck open)
- Purge solenoid hoses improper connection
- Improper operation of variable valve timing control system
- Fuel supply system malfunction or improper fuel line pressure
- Pressure regulator (built-in fuel pump unit) malfunction
- Fuel pump unit malfunction
- Fuel filter clogged or restricted
- Fuel leakage on fuel line from fuel distributor and fuel pump
- Ignition system malfunction
- Ignition coil related wiring harness malfunction
- Ignition coil malfunction
- Spark plug malfunction
- Improper operation of fuel injector
- Fuel injector malfunction
- Fuel injector related wiring harness malfunction
- Insufficient engine compression
- Misfire
- PCM malfunction
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