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OBD-II Trouble Shooting Got a code reader? Find out what your GM car's Check Engine light is trying to tell you (and then turn Check Engine light off).

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Old 09-23-2009, 10:43 PM   #1
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Default P0171


System Too Lean (Bank 1)

The oxygen sensor in bank 1 detected a lean condition (too much oxygen in the exhaust).

You will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a hesitation/surge on acceleration.

A code P0171 may mean that one or more of the following has happened:
  • The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled.
  • There could be a vacuum leak downstream of the MAF sensor.
  • Low fuel pressure.
Possible Solutions
  • In the vast majority of cases, simply cleaning the MAF sensor does the trick.
  • Inspect all vacuum and PCV hoses, replace if necessary, touch fittings, if your finger turns black, replace
  • Check for a dirty fuel filter, replace if needed, and proper fuel pressure
  • Check for loose sensors, MAF and IAC. The IAC has a O ring that should be checked.
  • Check intake manifold, injector "O" rings, EGR adapter,
    EGR valve, and EGR feed pipes for vacuum leaks. remove pipe and visually inspect.
  • Inspect EVAP purge valve for proper function.
  • Inspect battery cables for corrosion.
  • Inspect engine grounds.
  • Check exhaust system for corrosion, loose or missing
  • Test fuel pressure, key on, engine off.
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obd2, obdii, p0171, p171

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