| 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.
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| 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
- Fuel filter clogged or restricted
- Fuel return hose clogged
- 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
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