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.