P0172 and Weird Noise from Fuel Tank

[2006Ion2Red]

So I have had a P0172 code on my 2006 Saturn Ion-2 for a few months now. I know, it's been a while. My problem is that I can't seem to find out what is causing the car to run rich. Whenever I search leads for P0172 most say its the O2 sensor. I've replaced the downstream sensor because the value did not change when I monitored it on my scan tool, it stayed the same regardless of how the engine was running. After that was replace and code reset, the P0172 still came back. The upstream sensor seems to be running fine. Should I replace it still? Another thing I have noticed recently is that there is a sort of squeaking noise coming from the rear of the car. I raise up the back end and listened for where it was coming from and it is coming from the fuel tank. Could my pump be going bad? The car itself seems to run just fine. I tested the fuel pressure and it starts off a little over 50psi but then drops to about 45psi and holds. I'm just trying to find some clues as to what is going on. No one seems to know what the problem is. Any help would be much appreciated

[fdryer]

Mileage, maintenance done, parts replaced in addition to the rear O2 sensor?

P0172 does not suggest the rear o2 sensor as faulty. Rear o2 sensors always output steady signals since they're used to monitor catcon efficiency. The front precat O2 sensor varies output in direct relation to the feedback loop as it monitors exhaust gases; sending signals to the ecm/pcm will vary fuel mixtures with exhaust gases sensed in a continuous loop to fine tune emissions control, engine performance and fuel efficiency.

Some info may help with these attachments from the service manual, service bulletin and a general guideline from one site decoding OBD II codes; http://www.obd-codes.com/p0172

[2006Ion2Red]

Thanks for the info! I car has about 134,000 miles. I got the car when I had about 122,000. Shortly after I got the car it got an evap code (not sure which one). I replaced the fuel cap, evap vent valve, and evap purge valve. This solved the problem for that. I also got a really good deal on injectors so all 4 have been replaced. I also got a code for the IAC which is part of the throttle body and I replaced that. I have also replaced the fuel filter. All parts replaced were ACDelco except the fuel filter. I also cleaned the MAF sensor with MAF cleaner.
As for the rear O2 sensor, it's value didn't change at all. Not while driving and accelerating. Isn't it supposed to still have a wavy voltage read out? I read that it should and the new one does.
Thanks again for the quick rely!

[fdryer]

Well, unless you search for how O2 sensors operate, you're likely to be misinformed from anyone unfamiliar with the difference between exhaust manifold precat and post cat sensors. Google for info. One site I use is http://www.aa1car.com/library/o2sensor.htm. Its not the only site as there are many, including sensor manufacturers. The key to correct info is determining which ones are factual and easy to understand against sales tactics, testimonials, lies and any method to distract from basic info on how they work.

[Samtherecordman]

3 Knocks in the trunk, means your in business.... steeppppp On IT !!!!!

[Samtherecordman]

if your hearing noise... its most likelly the Saturn God Talking to you......... he talked to me a few times.... and he was always right.....