faulty fuel reading
I have a 2003 3.4L impala. Just got a code for the upstream oxygen sensor, picked up the part from the store and changed it. I filled up my tank, drove about 20 miles and the check engine light went off. After about 300 miles on the same tank it was still reading at full then it went to half and it was shifting shifting everywhere in between. Not sure whats going on but the gas gage isnt reading right.