[GTP Dad]

This may explain where to look:OBDII Error Summary related to Fuel Mixture
Code Detected Condition Trouble Area
P0171 System too Lean (Bank 1)

When air fuel ratio feedback is stable after engine warm up, fuel trim is considerably in error on the RICH side (2 trip detection logic) Air Induction System Leak
Injector Blockage
Mass Air Flow Meter
Engine Coolant Temperature Sensor
Fuel Pressure
Gas Leakage from the Exhaust System
Open or Short in the Oxygen Sensor or associated wiring
Oxygen Sensor Defective
Engine Control Unit

P0172 System too Rich (Bank 1)

When air fuel ratio feedback is stable after engine warm up, fuel trim is considerably in error on the LEAN side (2 trip detection logic) Injector Leak, Blockage
Mass Air Flow Meter
Engine Coolant Temperature Sensor
Ignition System
Fuel Pressure
Gas Leakage from the Exhaust System
Open or Short in the Oxygen Sensor or associated wiring
Oxygen Sensor Defective
Engine Control Unit

Check for a vacuum leak first then clean the MAF sensor with electronics cleaner, be gentle. The other causes are listed above and should be fairly straight forward to try. I hope this helps