DTC P0171: Notes
DTC P0171 DETECTION CONDITION AND POSSIBLE CAUSES
| DTC P0171 |
Fuel trim system too lean |
| DETECTION CONDITION |
- 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, PCM determines that the fuel system is too lean.
Diagnostic support note
- This is a continuous monitor. (Fuel system)
- 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 is available.
- DTC is stored in the PCM memory.
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| POSSIBLE CAUSE |
- Misfire
- Front HO2S deterioration
- Front HO2S heater malfunction
- MAF sensor malfunction
- Pressure regulator malfunction
- Fuel pump malfunction
- Fuel filter clogged or restricted
- Fuel leakage on fuel line from fuel delivery pipe and fuel pump
- Fuel return hose clogged
- Leakage exhaust system
- Purge solenoid valve malfunction
- Purge solenoid hoses improper connection
- Insufficient compression
- Variable valve timing control system improper operation
- Air suction in intake-air system malfunction
- PCM malfunction
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