so the D4 light on my dash does not light up what could cause this?

 

Blown bulb? Did you check that?

 

There is no air in my tire, what could cause this?

 

I don't think there is a D4 light bulb that can be replaced. Isn't the D4 light integrated onto the printed circuit board? The D4 light is controlled by two wires that run from the ECU to either the A/T indicator light in the cluster or the gear position switch in the console. The problem could be the switch, the wires, printed circuit board or the ECU.

 

So it would be a micro LED (notice I say would be). If it is blown you can solder out an old one and solder in a new one? I used to do it all the time when I modded computer parts.

 

You first need to show that the D4 light terminals in the cluster connectors get voltage and ground. If so, then you would typically replace the printed circuit board, or do the repair you mentioned, though I have not seen a DIY.