P0171

Description
System Too Lean (Bank 1)

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


Symptoms
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.
Causes
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
  hardware.
• Test fuel pressure, key on, engine off.