I was told i had bad o2 sensor i replaced both up and down stream still have the code then i was told it's the cat not the sensors so i replaced that today and still get p0171 code any idea what could be the problem dont what to keep throwing money at this thanks

 

Did you clear the code after sensor replacement? Who is performing the repairs?

 

Other than disconnecting the positive battery cable for 30 mins not sure how eles to do it.

 

I replaced them my self they were bosh parts from auto zone

 

Sorry man, P0171 means your running lean in bank 1. My bet is you have clogged injectors, not getting enough fuel. The code doesn't mean o2 sensors or cat problem. Get a can of bg44k on ebay or some local auto dealers have them for around 22 bucks. Use it, works very well. Will clean your injectors in one tank.

 

what year and engine. diagnosis is different depending if its speed density fuel metering or maf sensor controlled.
check the fuel trim.
need to know if its running lean at idle or at higher rpm, on both banks or just one bank. just because the dtc is setting for only one bank, doesn't mean the other bank isnt lean also...check with the scan tool.

if both banks are lean all the time, check fuel pressure. if its only lean at idle, you have a vacuum leak.