Ok I have been trying to get this dam check eng, light off in my truck for weeks

Let me start at the begining I had something break loose in my Cat. and it rattled all the time internally not the shield so I replaced it with new, While it was off the truck I had to move the truck in and out of the garage so Check Eng light came on. installed new cat and reset light and all good for about 3 weeks
'
Then light came on again this time I checked codes PO171 and PO174
Fuel trim Bank one and two Lean condition.


I have replaced both o2 sensors uppers on bank 1 and 2
replaced all spark plugs
clean air filter , Cleaned Mass air flow
replaced PVC
have run a can or 2 of injector cleaner through the tank
It is driving me crazy now I need to get through emmisions to get new tags
any idea can't keep spending money and not fixing the issue

Every time I reset the code before I did new plugs, light would stay off for a least three start cycles, now it comes on in about 4 mins

It could be fuel pressure is low but the truck really runs so good I am baffled I wonder if the new cat convert is bad I am almost to the point of reinstalling the old one and see if the light goes out.


Anyone have any idieas
HELP

 

Using the search button at the top of the pane and entering "p0171 p0174" I got three pages of threads.
Surely your answer must be in there somewhere.

 

yeah I have read those threads they all seem to jump around and not really giving a answer to the question as to what fixed the problem

 

cats wont cause lean codes. if they were pluged it would cause a rich code. u have to have a vacuum leak, mass air flow, low fuel pressure possibly. these are about the only thing that can cause both banks to throw these 2 codes at the same time.

 

While checking some past threads one thing stuck out.
4.0s seem to like to loosen the intake bolts quite a bit. Check to make sure they are tight.

 

I had the same set of problems early on as well, test your EGR valve, It did the trick for me for a long while. and it never hurts to check your fuel pressure. you can rent the tool from o'rileys or autozone

 

Sorry guys must have tyoe in the wrong Code the 1st time I searched after OTRtech reply I went back and researched again found it to be the same problem everyone else has been having. Thanks foe sending me in the right direction Ken Appeicate it.

 

here is the culprit Light is out and codes are gone,