Your fuel to air ratio is not right. It could be a number of different fixes.
Bank 2 running too lean.
P0171 System too Lean (Bank 1)
1999 Ford Taurus. System Adaptive fuel too lean banks 1 and 2. How can I fix these.
Your system is too lean. That's what it will say on obd2 scaner tool. It means that your air to fuel ratio is too lean.
A lean mixture is referring to the gas/air ratio. Lean being less gas
Too lean of a mixture. See if a jet is not clogged and clean the carb.
POST CATALYST FUEL TRIM SYS TOO LEAN BANK2
Your gas/air mixture is too lean. Adjust your carb to be more rich.
Trouble code P0174 means:System too lean (Bank 2)
The explosive range for natural gas is typically between 5% and 15% gas-to-air mixture. Below 5%, the mixture is too lean to ignite, and above 15%, it is too rich to ignite.
An engine runs by the combustion of a mixture of oxygen and gasoline. If this mix has too much oxygen, it is said to run lean. When the mixture has too much gasoline in relation to oxygen, it is running rich.
The flammability range of natural gas is typically between 5% and 15% in air. This means that natural gas will only ignite and burn within this specific range of gas-to-air ratio. Below 5% it is too lean to burn, and above 15% it is too rich.