I bought this car a month ago and now I have a code po171 and po174.
I`m planning on replacing my leaky valve cover gaskets so while I'm getting dirty why not address those pesky sensors. can someone advise me on what to do and where these guys are located.

 

P 0171 Possible causes
- Intake air leaks
- Faulty front heated oxygen sensor
- Ignition misfiring
- Faulty fuel injectors
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Faulty Mass Air Flow (MAF) sensor
- Incorrect Positive Crankcase Ventilation (PCV) hose connection

 

If the P0171 is combined with the P0174 code, it's very likely that the problem is caused by an intake leak. If there are no intake leaks, the next step is to replaced the air filter and clean the air flow meter. If the problem persist the front oxygen (O2) sensor may need to be replaced.

http://engine-codes.com/p0174_chrysler.html

I have a 2001 Chevy truck I bought new and it took awhile to figure it out why it was throwing all the codes, but once I pulled the intake off and cleaned it up. Put new rubber gaskets on it runs like a new truck. Only time it would throw a fault was when it was under heavy load, like pulling my trailer. That is when it faulted.

 

Something I found while doing a search for the problem you mentioned.

Re: code P0171 and P0174

Problem Solved
Figured I'd let others know what the problem was. Engine running lean and throwing the P0171 & P0174 codes due to small air leak. Only at idle would this symptoms appear. Ran great other wise. Searched and searched for leak using starter fluid on vacuum lines - found nothing. MAF sensor replacement didn't affect it. This rough engine at idle started soon after the oil change. Never put the two together.

On the oil cap is two triangles that one is to line up, I assume to indicate the cap is sufficiently tight. Well that was the issue. The triangles were lined up perfect. Problem was is the seal under the cap wasn't fulling mating with the surface (all the time) and was the source of the small air leak. The engine pulls a vacuum and was getting a little air from the oil cap. Had I tighten it like normal and not lined the triangles up, I would have never had then lean codes/engine running rough.

Local shop pressurized the engine via the intake with smoke of some sort and saw it coming out of the oil cap area. A new oil cap solved the problem. go figure.....