I just can't frickin win. I threw DTC codes PO171 and PO174 System to Lean Banks 1 & 2 tonight while I was just cruising around. So I am not going tomorrow because I have to check a bunch of things to see what caused the code. Here is my list. I am not getting this done tonight.

Air Measurement System
  • MAF sensor (contaminated, damaged, malfunctioning, etc.)
Fuel System
  • Fuel pressure regulator (leaking, malfunctioning, etc.).
  • Fuel filter plugged, dirty.
  • Fuel pump (weak, check valve leaking, etc.).
  • Leaking/contaminated fuel injectors.
  • Low fuel pressure or running out of fuel.
  • EVAP canister purge valve leaking (when canister is "clean").
  • Fuel supply line restricted.
  • Fuel rail pressure sensor (incorrect reading).
Air Induction System
  • Air leaks after the MAF.
  • Vacuum Leaks.
  • PCV system (leak, valve stuck open, etc.)
  • Improperly seated engine oil dipstick.
Exhaust System
  • Exhaust leaks before or near the HO2Ss (exhaust manifold gasket, mating gaskets, etc.)..
EGR System
  • EGR valve tube/gasket leak
  • EVR solenoid vacuum leak
Secondary Air Injection
  • Damaged/malfunctioning secondary air injection system (mechanically stuck valve).