Generally, the lense has small tabs on it that can be gently pried out to get access to the bulbs.
There are no bulbs, it is a panel of mini-lights. You access this from the trunk area.
Remove the entire headlight assembly to gain access to the bulbs.
If you can not remove fasteners on outside, you may need to cut a section out of the inside of trunk to get your hand by the bulbs.
you open the trunk. Pull back the carpet covering the back side of the taillights. Remove the plastic wing nuts, about six or eight. Slide the whole taillight assembly to the rear. The bulbs pop out of the assembly for an easy replacement.
Bulbs cannot be replaced. Entire control module must be replaced.
I had the same problem with my 87 Riv. It was a burnt out bulb in the rear of the car. My front signals did work and as they run on different circuits, check and replace the bulbs. Access to the back lights are inside the trunk back.
open trunk there are six hand tightened plastic wing nuts undo all of those the entire assembly will come off then you may change bulbs
Open the trunk and there should be several small bolts or wing nuts that can be removed. Then the entire center housing can be removed, twist the old bulbs out and replace.
-- Without changing the bulbs, increase the voltage of the battery or power supply. -- If the bulbs are in series, take one out of the circuit, and replace it with a piece of wire. -- Replace incandescent bulbs with others whose filaments have lower resistance. -- Replace incandescent bulbs with fluorescent tubes. -- Replace incandescent bulbs with LEDs.
The side marker bulbs on a 2002 Buick LeSabre are replaced by removing the retaining screws and disconnecting the wiring harness. The old bulb can then be removed and a new bulb put in its place.