P0171 TOYOTA - Air/Fuel Mixture System Lean Bank 1

Possible causes

  1. Intake air leaks
  2. Faulty front heated oxygen sensor
  3. Ignition misfiring
  4. Faulty fuel injectors
  5. Exhaust gas leaks
  6. Incorrect fuel pressure
  7. Lack of fuel
  8. Faulty Mass Air Flow (MAF) sensor
  9. Incorrect Positive Crankcase Ventilation (PCV) hose connection