What does Nissan Maxima code P0446 mean?

Answer 1

The evap code is probably the gas cap being loose. Make sure your gas cap is good and be sure to tighten it when you get gas or the light will come on. If that is not it there is a charcoal cannister that has a vent valve that has gone bad. Check the gas cap first.

The idle control system is probably the throttle position sensor or the idle air control valve. I would go with the throttle position switch first as it is cheaper. If you have a service manual you can look up the voltage values on both and check them before replacement. Basically, the computer is saying the idle is out of range and it cannot bring it back to where it should be. Make sure your car is tuned up before you start replacement of these parts. If you have not done a tuneup in a long time that could be another cause so do this first reset the codes and drive it and see if the codes come back.