P0171 & P0174?
Engine running lean means exactly that, it's not getting enough fuel or it's getting too much air. This is being reported to the PCM by the O2 sensors.

Usually you're looking for an air leak after the MAF sensor, possibly the intake manifold. How long have you had the CAI on there? Also, make sure any vacuum lines from the intake are connected and in good shape.

A malfunctioning fuel pressure regulator or weak fuel pump can give you weak fuel pressure.

It's also possible that the O2 sensors are bad. Don't run out and buy them, it's not the likey cause.

Start with the free stuff, check the clamps on the CAI and all the vacuum hoses on the intake. Check fuel pressure. Check for intake leak by spraying propane or starting fluid around the intake especially between the intake and the heads. If there's a leak you will hear a slight bump in the rpm's.

 

Yup, it's P0171 & P0174.The codes only started showing up after I put in my oil catch can. I've checked the hoses from the pcv valve to the catch and from the catch can to the intake. I can't find any leaks.

The C.A.I.could be the culprit... It's kind of forced onto the throttle body at a weird angle because of the lack of room from the throttle body spacer. But, like I said, the codes only started showing up after the catch can was install, which was a few months after I put in the TBS.

 

I'd have to say that the catch can is the prime suspect, leak or not. You could try getting an idle air relearn.

 

If it isn't a huge ordeal I would pull the catch can out and go back to just the intake and see if that solves the problem and if not back to completely stock. Like Silver Surfer said, try the stuff that just costs you time and not money first.

 

I've tightened all the clamps around the hoses and the codes will go away for a while but end up coming back on. I paid a decent amount for the catch can so I really don't want to take it out. Are the codes that much of an issue?

 

They are when you go to emissions and they usually indicate a performance problem.

 

Well, I've rechecked all of the hoses and tried disconnecting the negative battery cable (I read somewhere that this might help). It took the light off, and has remained off for the past couple of days. Knock on wood...

 

You should be able to check the intake gaskets by spraying some carb cleaner around them while the truck is running. If it sputters they are in need of replacing. When mine went bad, the codes were intermittent as well.

 

Just occurred to me, when I first got my truck I popped a couple of lean codes (171/174). When that happened I remembered seeing that occasionly when the fuel tank is kept below 1/4 tank. I cleared the codes and kept the fuel gauge above 1/2 and the light hasn't come back, and it's been months. Just a thought.