2001 Ford Taurus Diagnostic codes PO171 & PO174

I have a 2001 Ford Taurus and it recently set these two codes. I was told that it may be in the MAF sensor or PCV. Could someone tell me if this is correct? or if not guide me to fix this problem. Any help will be greatly appreciated Thank you There are a lot of things that can cause those codes. That is for both banks being lean. Below are some possible causes.

For lean and rich DTCs:

• Fuel system
• Excessive fuel pressure.
• Leaking/contaminated fuel injectors.
• Leaking fuel pressure regulator.
• Low fuel pressure or running out of fuel.
• Vapor recovery system.
• Induction system:
  • Air leaks after the MAF.
  • Vacuum Leaks.
  • PCV system.
  • Improperly seated engine oil dipstick.
• EGR system:
  • Leaking gasket.
  • Stuck EGR valve.
  • Leaking diaphragm or EVR.
• Base Engine:
  • Oil overfill.
  • Cam timing.
  • Cylinder compression.
  • Exhaust leaks before or near the HO2Ss

Being way2old is why I need help from younger minds Thanks very much for the help and quick response. With the list you gave me I'm not sure exactly what to do, is thereany way to narrow it down further? Thanks
Which engine do you have? From left to right, what is the eighth digit of the VIN #? U, S, 2?
Loren
SW Washington A scan tool that will read live data is about the only way to narrow it down quickly. Other than that, usually the top of the list is the most frequent cause and work your way down the list. Most of the time if you get both banks lean, look for something that will affect both sides of the engine (vacuum leaks, low fuel pressure, air leaks after the MAF. possibly the MAF itself.) If fuel pressure is not low, then go to the air induction system. These checks are the same for lean or rich conditions.

The engine is front to back and the vin is a u. Thanks for all the good information, I hope I can solve it from what you have listed. I appreciate all the help!
Thanks for the reply.. VIN U...blows my theory.
Loren
SW Washington You said it blows your theory, what was your theory? Is it something that can help me? Thanks
No, sorry. I was thinking IMRC leak, but your's doesn't use it.
Loren
SW Washington I have a scan tool that reads live data, what should I be looking for that will help me narrow it down? Your help is greatly appreciated