ive got an Auto Climate Control. and ive got a few questions.

1) when i switch modes using the button, i hear a noise low buzzing sound. is this normal?

2) i recently have a problem with my maxima, and i have no CEL and the car is jittering. for ex., I'm at a stop light and the light turns green, i let off the brakes, and i hear the same noise i hear from the Auto Climate Control, and the idle feels like someone stepping on the brakes rappidly. when im driving at high speeds like 55MPH or above, it feels okay but not 100%. This problem seems to be off and on. But More ON than OFF

can anyone help?

Thanks A Lot

 

i just checked the codes, no CEL and it says i have a bad knock sensor. and 0504 Auto Trans Comm Line. says possible cause is discharged battery, ive been using my laptop in my car recently and does anyone think this code will clear after the battery recharges?

thanks