With all switches unhooked, so headlight, doors, and map switch, pull the bulb and get an ohmeter reading to ground from the yellow wire. Should be infinity.
Then take the bulb in hand and measure from each bulb terminal to the bulb shell Both terminals should be infinity to the shell. Keep your fingers off the probe tips
THE BULB DOES?? have?? two terminals, right?
Should be a 1004 bulb like this............