Probably what he ^^ says then, it has to be one of these two only other possibility which would be very strange is if the live to the bulb has gone astray.

Not sure of the type of bulb but on Sierra it has a white plastic knob on the end, imagine yours would be similar (The same as rest of warning lights, bar ABS) which you twist so you can then remove it (Two lugs holding it) it would just be a standard 12V low wattage bulb.

NB With ignition off and 12V sent down the blue wire the bulb should illuminate.

Martin