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DTC P0171, P0174: System Too Lean: Notes

DTC P0171, P0174 CHART (MZI-3.7)

DTC P0171 P0171: System too lean (RH)
DTC P0174 P0174: System too lean (LH)
DETECTION CONDITION 
  • P0171 indicates that the fuel/air ratio is too lean (RH).
  • P0174 indicates that the fuel/air ratio is too lean (LH).
  • The adaptive fuel strategy continuously monitors the fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit.
POSSIBLE CAUSE  Fuel System:
  • Damaged or leaking fuel pulse damper
  • Leaking fuel pump check valve
  • Ethanol content in fuel
  • Fuel supply line restricted
  • Damaged or leaking fuel pulse damper
  • Fuel filter plugged or dirty
  • Low fuel pressure or running out of fuel
  • Purge solenoid valve is leaking when the canister is clean
  • Leaking/contaminated fuel injectors

Exhaust System:
  • Exhaust leaks in the exhaust manifold gasket or mating gaskets before or near the A/F sensor

Intake Air System:
  • Vacuum leaks
  • PCV system is leaking or the valve is stuck open
  • Air leaks after the MAF sensor
  • Improperly seated engine oil dipstick
  • Intake air turbulence due to incorrect air filter
  • Contaminated MAF sensor

Electrical System:
  • MAF sensor malfunction
  • PCM malfunction
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