3.4l P0171 code

im beating a dead horse I know. So on my 99 it threw this code. I cleaned the MAF and replaced it actually and it was still there. So checking live data on a regular scanner it shows my o2s11 voltage to be 0.015 at idle. Bad upstream A/F sensor? I know this is a common thing but I’m just wondering if anyone else has had this problem. That voltage should be higher right? When reving the engine up, it’ll climb but will come back to 0.015.