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OBD-II · Motor och drivlina (P)

P0171

System too lean bank 1

Vad den betyder

Bank 1 is running with too much air or not enough fuel.

Symtom

  • engine warning light
  • hesitation or flat spots when accelerating
  • rough or hunting idle, sometimes stalling
  • may be worse when cold or at idle

Troliga orsaker, den vanligaste först

Troliga orsaker, den vanligaste först
No.Orsak
01vacuum leak, often a failed crankcase breather (PCV) valve or split intake hose
02dirty or failing MAF sensor under-reading air flow
03low fuel pressure (weak pump, clogged filter)
04exhaust leak before the lambda sensor
05LPG system running lean on converted cars

Vad du ska kontrollera, steg för steg

  1. 01Read short- and long-term fuel trims at idle and at about 2,500 rpm: high trims at idle that improve with rpm point to a vacuum leak; high trims at all speeds point to fuel delivery or the MAF
  2. 02Smoke-test the intake and check the crankcase breather/PCV valve (a whistle or strong suction at the oil filler cap is a clue)
  3. 03Compare MAF readings with OEM values; clean only if permitted by the sensor maker, otherwise replace a confirmed faulty sensor.
  4. 04Check fuel pressure and delivery (pump, filter)
  5. 05On LPG-converted cars, check whether the trims are normal on petrol; if so, service or recalibrate the gas system
  6. 06Check for exhaust leaks before the upstream lambda sensor