[hinton08]

Usually a P0171 can be a faulty oxygen sensor, but first I would check for a few things :missing, loose, or leaking exhaust components, forward of the O2 sensor, vacuum leaks at the throttle body or injector o-rings for leaks, air induction system and air intake ducts for leaks, check the secondary air injection (AIR) system for leaks, improper air delivery, shut off valve not closing, or crankcase ventilation system for leaks. In order to check the O2 sensor, you need either a live data scan tool or a multimeter to watch the O2 sensor readings. Readings should fluctuate between about 200mv and 800mv. The reading should fluctuate back and forth constantly. If the fluctuation seems slow and sticks, replace the O2 Sensor. Like I said, the O2 sensor will probably fix it with the mileage on the vehicle, but I'd do a quick look over of the places mentioned above to ensure there are no vacuum or exhaust leaks. Hope this helps!