It means that your engine is running lean - not getting enough fuel for the amount of air that the engine is receiving. Because your maxima is equipped with a V-6 engine, whatever the problem, it is affecting only bank #1. Bank #1 is always the side of the engine where cylinder #1 is located, or in your case, the left side of the engine as it is viewed while facing the crankshaft end of the engine.
(on a 4 cylinder engine, there is only one bank and it is always referred to as Bank #1)
There are several things that can cause a lean condition including vacuum leaks, a malfunctioning Evaporative Emissions system, a misfiring cylinder (due to bad plugs, bad injectors, or an intake or head gasket leak.), a malfunctioning Mass Airflow sensor (MAF) or Manifold Absolute Pressure sensor (MAP) or even a bad Oxygen sensor (O2s) (Nissan sometimes calls an O2s an "Air-Fuel Ratio Sensor") It is even possible for a leaking vacuum brake booster to cause a lean code.
If there are any other malfunction codes present, it may help to pinpiont the cause of the lean code. (Like a P0301 "cylinder#1 misfire detected", in which case, you would address the misfire code first.)
Certain problems, like a leaking brake booster or a bad MAF will usually set lean codes for BOTH banks.
If the P0171 is the ONLY code present, the most likely cause is a bad O2s, but I recommend some diagnostic testing to prove it before spending the mega-bucks that Nissan gets for their O2 sensors.
Hi my name is nizam , i have 199 nissan maxima i just change 02 sensors than come up po171 what is the problem
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