The check engine light came on and codes popped up code p0507 saying the rpm is idleing to high and code p0171 saying bank 1 system to lean...sounds like a 02 sensor i already replaced bank 1 sensor 1 but never replaced bank 1 sensor 2 could it be a bad o2 sensor thsts causing a problem? Some people are saying it might be the throttle body is dirty but i cleaned it not to long ago and i did pop open the butterfly valve thing so maybe i have to so the idle relearn procedure i dont know

 

for the P0507, see page 433 in this link:
http://boredmder.com/FSMs/Nissan/Maxima/2003/EC.pdf

DTC P0171 is for the bank 1 sensor 1 oxygen sensor. Bank 1 sensor 2 has a different code. How long ago did you replace the sensor? But whatever it was, it appears to have gone bad. I don't know what brand you put in, but I would suggest you use the Bosch brand.

 

I literally replaced bank 1 sensor 1 like 100 miles ago with the oem bosche sensor so it cant be that maybe its the second upstream because no its saying bank and i did the idle relearn trick about turning the key and pressing gas etc and the car idles normal i reset the code so I'm going to give it a couple days but that lean bank thing worrys me what bank is the second upstream i hear its behind the engine on the back header is that bank 2 sensor 2?

 

Bank 1 is the firewall side Bank2 is the radiator side...


Perhaps you could exchange the o2 sensor if it has warranty

 

Im sorry it was bank 2 is lean but isnt rhat downstream? The upstream is more important right?

 

Well, you gave us code P0171.
P0171 is for bank 1 sensor 1.
P0174 is for bank 2 sensor 1.

And like Nestor said, bank 1 is next to the firewall. Bank 2 is next to the radiator.

Yes, the upstream sensors will have a more detrimental effect on the car's performance than the downstream sensors. Downstream sensors won't have any effect on performance. What Nissan calls sensor 1 is the upstream sensor. Sensor 2 is the downstream sensor.