Codes, p0171 and p0174

my 4.0 aurora is thowing these codes, which are for running lean in the left and right bank. Any idea what might cause this, or how i should go about trouble shooting the problem?

any ideas? I was thinking a possible o2 sensor problem, but i really don't know how to test them to see. I'm open to any suggestions

If you are running lean in the left and right bank then it is most likely not your sensor failing, rather the sensor is telling you that something is wrong, probably with the whole engine, which is good. (good because its probably not a single cylinder) This code says that the ECM is unable to keep the car from running in a lean state. If the computer detects a lean state it generally fixes it by putting more fuel in but in your case the ECM is unable to richen the system to the desired state. I would have your fuel pressure checked.