What does trouble code P0171 for a 2002 Buick Park Avenue mean?

Trouble Code: P0171 (3.8L V6 VIN 1 Auto)
Fuel Trim System Lean (Bank 1) Print this code data Number of Trips to Set Code: 2
OBD II Monitor Type: CCM Details
Indicators: MIL Details

• Fuel Details
• MIL Details

Trouble Code Conditions:
DTC P0101-P0103, P0107, P0108, P0121-P0123, P0130-P0138, P0140, P0141, P0201-P0206, P0300, P0401-P0405, P0410, P0440-P0446, P0506, P0507, P1404 or P1441 not set, engine started, vehicle driven at less than 82 mph at 550-4000 rpm, BARO sensor over 70 kPa (10.1 psi), ECT sensor from 68-230ºF, IAT sensor from 64-158ºF, MAF sensor from 2.8-150 gm/s, MAP sensor from 16-105 kPa (2.6-15.2 psi), fuel level over 10%, and the PCM detected the Long Term fuel trim value was more than +20% for 6 seconds. The PCM controls the air/fuel metering system to good overall fuel economy, driveability, and emission control. During open loop, the PCM determines fuel delivery based on sensor signals, without the oxygen sensor input. During closed loop, the PCM adds oxygen sensor inputs to calculate Short and Long term fuel trim fuel delivery adjustments. Short Term fuel trim values change rapidly in response to changes in the oxygen sensor signals. Long Term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1.

Possible Causes:

• Air leaks in intake manifold, exhaust pipes or exhaust manifold
  
• Fuel control sensor is out of calibration (ECT, IAT or MAF)
  
• Low fuel pressure (fuel filter clogged, pressure regulator failure)
  
• One or more injectors restricted or pressure regulator has failed
  
• HO2S element is contaminated, deteriorated or has failed
  
• Vacuum hose is disconnected, broken, leaking or loose
  

Troubleshooting:2002 Buick Park Avenue, 3.8L, P0171