ok...I ordered all three oxygen sensor for my maxima through courtesy nissan. I did have the follow codes tripped.....

0503
0303
0304

the first two are the front O2 sensors. The last one was the knock sensor. I have replaced everything (knock sensor included). I now have the following codes....

0503
0303
0901
1001

I replaced the 02 sensors myself and was still getting the 0503 and the 0303 codes even after clearing the computer (along with 0304). I just had the dealer replace my knock sensor for $65 and now I am getting 0901 and 1001 but no 0304. Anyone have a clue as to the problem? Could the tech have forgotten to hook back up the heated O2 sensor heaters for the left and right front? Are they anywhere close to where the knock sensor is located?

Thanks,

Rutnick