I swapped my 2001 head unit with a 2002 one, it plays CDs fine, but the issue is I cannot change bass, treble etc. When I press the knob, it shows bass, treble but when I turn the knob, it won't change. Can someone suggest what could be wrong? Thanks for your help in advance!

 

Go to autozone or something and buy some electronics cleaner spray.

Pull the dial knob thing straight out. You'll see a metal thing sticking out. Spray the cleaner at the base of that thing, and try to get clean it properly.

Hold some paper towel under the knob to catch the runoff.

If that don't help, it's broke