p0171 code

[firefighter407]

got a 99 expedition EB with a 5.4,

the service engine soon light came on and I got a P0171 code (#1 bank lean) would this be caused by a bad o2 sensor? I've never changd them and i think they are still the originals. if the left side are bad how can I check them? I think I got 4 sensors.

Thanks

 

[ChuckD]

The code can tell you what the problem is but not what is causing the problem. I would start at cleaning the MAF and reseting the code and see if it comes back. If it does then I would go and isolate injectors.