Iv got a 2003 4.8 chevy pickup i replaced the MAF and both O2s and its still reading that its all three and its running lean

code p 0171 refers to system too lean bank 1=== causes ---intake /exhaust leak---AIR system--MAF/VAF sensor---fuel pressure/pump---injector/s---heated oxygen (HO2S) sensor
the HO2S is the unit that controls the mixture and is located in the exhaust manifold / pipe before the cat converter

the oxygen (O2S) is just like a final trim and reads the cat converter operation and is located after the cat converter

bank one is closest to the fire wall

Lean banks 1 & 2. Most likely a vacuum leak, but could be a dirty or bad MAF sensor, clogged injector(s), bad O2s(although I doubt 2 go bad at the same time), etc.
Those are always fun to diagnose. I would focus on the vacuum hoses and try cleaning the MAF elements with CRC MAF cleaner or electrical contact cleaner.

Sounds like the Mass Air-Flow Sensor may be toast. I think you are on the right track. My scanner does not see MAF either. good luck.

P0171 and P0174 are lean codes. There is likely a large vacuum leak or the MAF is bad.

Try starting the car and wiggling the connector for the MAF sensor. Also try tapping the MAF sensor. If the idle changes or the car stalls replace the MAF sensor.

The second shop should recognize that these codes don't have anything to do with the ignition module.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

-25 LFT? your dealing with a fuel injector that is leaking or not atomnizing, Inspect the fuel pressure vacuum line is fuel coming out of the pressure regulator?

Hello! Lets look at this with cause and effect...One of only a few sensors is the cause of a lean mixture...The lean mixture then causes random misfires which in turn causes the O2 sensor to read to much oxygen in the exhaust...

Two sensors control the fuel/air mixture; The Mass Air Flow (MAF) and the Manifold Absolute Pressure (MAP) sensor...Lets eliminate..You'll need an multimeter (digital is best...$20)...The MAF is bolted to the inlet hose to the throttle body...See drawing below...It is combined with the Intake Air Temperature sensor...Pull the connector...Set meter to read 50K Ohms...Locate the pins where the wire colors Gray and Gray/Red connect...Clip meter leads to these pins on the unit...At 77 degrees F you should read 36K ohms...with a hot engine 190 degrees F should read 3.5 K ohms...Notice how as temperature rises the resistance drops...If you do not get these readings the MAF with IAT is the problem...Replace it...If it reads as specified here is the next test...Buy a can of electronic contact cleaner (auto parts store) Remove the MAF from the intake hose...Spray into the air passage...Cleaner leaves no residue and dries quickly...Install, plug in connector and test...If fault has cleared stop there and let me know...NOTE: Using an after market air cleaner that is impregnated with oil will ruin the MAF sensor...Send a comment...Guru...Saailer

I’m happy to help further over the phone at https://www.6ya.com/expert/david_6df67de3b14de867

how about a PO133 ,,,should be the first in system

Schematic
The Oxygen Sensor 1 (O2S-1) is an electrical source that responds to oxygen content in the exhaust manifold. When the sensor reaches approximately 316°C (600°F), it produces a voltage based on the difference in oxygen between the atmosphere and exhaust gas. The PCM sends a bias voltage (391-491 mV) on the signal line which is pulled up through high resistance. When the O2S-1 is cold, it produces no voltage and has extremely high internal resistance. The internal resistance of the sensor is much greater than the resistance of the bias pull-up resistor. However, when the sensor heats up, it produces voltage that overrides the bias voltage. This voltage is read by the PCM to determine a rich/lean O2S-1 signal used to adjust injector pulse width. Under normal conditions, low sensor voltage means high oxygen content/lean air-fuel mixture and vice versa. Normal sensor readings will fluctuate between 10 mV and 999 mV DTC P0133 sets when the O2S-1 signal rich to lean or lean to rich average response time is too slow.

DTC PARAMETERS
DTC P0133 will set if the average response time of the LEAN to RICH switches is greater than 125 ms or the average response time of the RICH to LEAN switches is greater than 156 ms for 100 seconds when:
^ Engine speed is between 1500 and 3200 RPM
^ Loop status is closed
^ Calculated air flow is greater than 7 gm/s
^ Commanded air/fuel ratio is 14.7 to 1
^ No cam, CKP, ECT, EGR, EVAP purge solenoid, fuel trim, IAT, MAP misfire, system voltage or TP sensor DTCs have been set.

DTC P0133 diagnostic runs continuously once the once the above conditions have been met.

DTC P0133 is a type B DTC.

DIAGNOSTIC AIDS
Possible causes of DTC P0133:
^ An intermittent connection or corrosion in the O2S-1 harness connector can set this DTC. Use Scan tool to monitor O2S-1 voltage with engine running at normal operating temperature while wiggling the signal and ground wire. Make sure the sensor is tight.
^ The most probable cause for DTC P0133 is contamination. Check for obvious contamination (oil, fuel or engine coolant) by removing sensor. Identify and correct the cause of the contamination if contaminated. Replace the O2S-1.
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Lean is an air leak after the MAF.

The MAF is telling the computer how much air there is by density and temp. The computer adjusts the Fuel Map according to the air density and temp. If there is air that enters the intake without the MAF seeing it first, the result will be not enough gas, which the O2s will report back as a lean condition.

The MAF will be telling the car that there is a certain quality -- density and temp -- of air, and the injector timing is set for that quality. New air comes in that the MAF has not seen, and now the fuel map is not opening the injectors long enough. You are probably looking at the lower intake boot being cracked causing the excess air to enter without the MAF sensing it. It's a common malfunction on our cars. Go to youtube and type E46 ICV and you'll see a video showing the intake area (from Xionunjust I believe). You can do this yourself a save a boatload of money. Take care of it quickly because severe damage can occur due to overheating (if ignored). If this helps can you please rate it. Thank you.

try replacing the fuel regulator,that would make it get too much fuel and the code for o2 sensor will come on saying too lean or too rich fuel mixture,and it would run rough

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.