How did your son install the ambient lights? Did he do it the plug and play method or have any slicing and soldering done?
Did you check the pressure in the full sized tires? The TPMS light will go off if one of those are below 28 PSI; the spare wouldn't have anything to do with this since it doesn't have a sensor. (At least mine doesn't)
If you have to go to a dealer to figure out the problem, keep this law on your mind. Basically its a law stating that a dealer cannot void your warranty if an aftermarket part is present and/or not the cause of a malfunction. Your warranty may be honored because to the best of my knowledge the lights are a Honda product for either the JDM (Japanese sepc) or CDM (Canadian spec) Fits.
Magnuson-Moss Warranty Act - Wikipedia, the free encyclopedia