I have an 2003 4.6L F150 Supercrew that I am having some trouble with a P0171 code. I have Dash Command and the Long Term Fuel Trim on bank 1 is running about 28-29% and doesn't change much while I have been driving it.

I am thinking that it might be the bank 1 O2 senor, but when I checked the voltage on the sensor it see some voltage fluctuation, but not sure if it's working properly.

Any other thoughts?

thanks
Mark