It has it's own bulb.

To see if it's even getting powered, you can try this:
There is a blue 22-pin connector under the kick panel on the driver's side (there are many connectors, this is the only blue 22-pin one.). Look for a yellow/black wire. This is the wire that applies voltage to the "D" bulb. Make sure that it has a potential on it when the shift lever is in "D" (get an assistant).

I only have a block diagram, not schematics, so I can't tell if this is a switch to ground or not.
Here are some other indicator lamps on the same connector that you can check and compare it to:
Park -red/black
Reverse -red/blue
Neutral -yellow/violet