Rear brake lights inoperative . The upper brake light on trunk deck works, but the lower lights in the main assemblies are inoperative.

Instructions

1. • 1 Open one of the rear doors of the LS. Position yourself on your knees in the back seat, facing the rear deck or rear dash.
     
   • 2 Remove the cover from the high-mount brake light assembly, by hand. Pull the cover toward the front of the vehicle. Do not pull extremely hard, or you will break the clips that mount through the deck from the trunk.
     
   • 3 Pull the old light bulbs out of the high-mount assembly. Wrap the new bulbs in a paper tower prior to picking them up. Insert new bulbs into the assembly, by hand. Do not touch the bulb lenses with your hands directly.
     
   • 4 Install the high-mount cover onto the rear deck and push the cover toward the rear glass to lock it in place.
     

Read more: http://www.ehow.com/how_10060583_replace-upper-brake-bulb-2001-lincoln-ls.html#ixzz30cNQ559F

What you want to do is open the trunk and remove the fasteners that hold the trunk lining to the rear deck panel and separate the lining from the deck panel.Disconnect the lamp wiring from the wiring harness.Now you will see some nuts that hold the tail lamp to the lower deck and the quarter panel.Remove these bolts or plastic wing nuts and remove the assembly from the car.To change the bulbs twist the socket and pull the socket and replace the bulb.Just reverse the process to put it back in.

From autozone.com. Please let me know if you have any questions.

1. Release the trunk latch and open the trunk lid.
2. Remove the fasteners holding the trunk lining to the lower rear deck panel.
3. Separate the trunk lining from the deck panel.
4. Detach the lamp wiring from the wiring harness.
5. Remove the nuts that retain the tail lamp to the lower deck and quarter panel.
6. Remove the tail lamp from the vehicle.
7. Remove the socket and pull the bulb out if replacement is needed.

To install:

1. Push a new bulb into place if required, then insert the socket into the lamp.
2. Insert the wire harness through the hole in the lower deck panel.
3. Install the wiring harness grommet into the lower deck panel.
4. Place the tail lamp into position on the vehicle.
5. Install the nuts to hold the lamp to the lower deck and quarter panel.
6. Attach the wire from the lamp to the body harness.
7. Place the trunk lining into position on the lower deck panel.
8. Install the fasteners that hold the trunk lining to the lower rear deck panel.
9. Check the operation of the lamp.

If the upper center works then the switch at the brake pedal is working properly. Maybe only two of the taillights are equipped with dual filament bulbs. If this is the case ( and it usually is) then you have two burnt out brake bulbs. They are dual filament and only one is lit (the lower intensity one) when the lights are on. Then the higher intensity filament lights when you hit the brakes. Open your trunk and take one out and look at it. Sometimes you can see the filament just hanging in there unconnected to one of the two posts. That means it is burnt out.

Rear Turn Signal, Brake and Parking Lights

1. Open the trunk and remove the luggage compartment trim.
2. Remove the eight nuts retaining the reflector to lower back of luggage compartment
3. Remove the rear panel reflector assembly from the vehicle. To install:
   
4. Installation is the reversal of the removal procedure. Fig. 8: Pull the trunk trim away from the lamp housing assembly
   Fig. 9: Twist the socket assembly and remove it from the housing
   

The procedure is as follows:-- Working from the trunk:
1. locate the 2 retaining knobs (doohickeys that you fasten the trunk cargo net to) for the Hard plastic trunk liner near to and inside of the rear light assembly. Unscrew the knobs.
2. Pulling back the plastic liner, locate the 4 studs (threaded posts). 3 will be located vertically in a line, the fourth, outboard and lower. Using a 10mm wrench(small), remove 3 of the 4 nuts fastening the light assembly to the body. DO NOT remove the lowest nut of the 3 in a vertical line, as this does not fasten the light assembly. DON'T LOSE THE NUTS OR WASHERS.

Working from the rear of the car:
1. Hand pull the light assembly from the car body.
2. Remove bad lamp. Twist lamp socket and pull out of assembly. Pull lamp and replace with #3057.
Reassemble:
1. Test light prior to reassembly.
2. Ensure Gasket material for assembly and studs is intact, this keeps water/dust out and dampens movement (prevents rattling and increases the life of lamp).
3. Use Reverse instruction for reassembly. -------------- The taillight/backup light/license plate light assembly is separate from the brake light/turn signal light assembly on the Buick LeSabre. No matter what rear bulb you have to replace, you must access the trunk area to do so. Open the trunk of the Buick LeSabre.Locate 7 nuts underneath the trunk lid (3 on each end of the trunk lid and 1 in the middle). Remove each one using a nut driver.Manipulate the trunk lid at chest level and gently pull the rear taillight assembly slightly away from the trunk lid.Locate the burned out bulb sockets and then remove the bulbs. Insert the new bulbs into the socket and test by turning on the lights before reassembling.Replace the tail light assembly by aligning the studs inside the predrilled holes in the trunk lid. Refasten the 7 nuts.Remove the cargo net if applicable to replace the brake and/or turn signal light.Unscrew the plastic wingnut that the cargo net is attached to. Pull back the trunk liner.Remove the 2 plastic wingnuts under the trunk liner.Pull the brake light assembly outward from the back of the LeSabre.Locate the socket of the burned out bulb and then turn counter clockwise 1/4-inch to release it from the assembly.Remove the old bulb from the socket and replace with a new one. Test the light before reassembling. Thanks. Keep updated for any more query. You can rate this solution and show your appreciation.

pop the trunk and right behind where the lights are pull the carpet down and their will be of the following depending on the trim.

You will either see the light sockets themselves that you can twist and pull to change the bulb, or you will see the plastic nuts/screws that you can remove to remove the entire assembly in order to access the bulbs.

If it's your 3rd brake light, the screws to access the housing are located in the upper part of the trunk

Brake Shoes Removal & Installation To Remove:

1. Raise and safely support rear of vehicle.
2. Remove rear wheel assemblies.
3. Release parking brake.
4. Remove brake drum.

Rear brake shoe assembly

1. Using an appropriate brake spring tool, unhook upper return spring from rearward brake shoe.
2. Push retainer springs IN and turn to remove tension pins.
3. Lower brake shoe assembly and remove lower return spring.
4. Remove brake shoe assembly from back plate.
5. Disconnect parking brake cable from lever and remove brake shoe.
6. Remove parking brake lever from brake shoe.

To Install:

1. Install parking brake lever to rearward brake shoe.
2. Secure lever to brake show with a NEW U-clip.
3. Pinch U-clip closed.
4. Connect parking brake cable to rearward brake shoe.
5. Install self-adjuster lever spring on front brake shoe.
6. Assemble clevises, adjuster bolt and upper and lower return springs.
7. Apply a light coat of grease (Molykote 44MA or equivalent) to sliding surfaces.
8. Install brake shoe assembly onto back plate.
9. Install tension springs.
10. Using an appropriate brake spring tool, unhook upper return spring to rearward brake shoe.
11. Install brake drum.
12. Install rear wheel assembly.
13. Lower vehicle.
14. Adjust self-adjusting brakes by pressing brake pedal several times.

are you sure bulbs are good ?? double check bulbs also make sure there is a ground wire from your light fixture is grounded to the body near by this might be causing your problem .. usually if front ones blink fast rear bulbs are bad ... thanks Jerry holler if you need more.

This is how i did it on my 2006 Sonata

1.) unplug the connector in the trunk (its a small white plug running up to the third light, there should be a small clip you squeeze).

2.) remove the 2 gold-colored screws from inside the trunk. They can be seen from the trunk. 1 is thru the larger square opening where the wire connects to the 3rd brake light. The 2nd is on the right side thru a small (screwdriver width) hole covered by a piece of foam tape stuff I had to punch me screwdriver through the foam to get to it.

3.) after removing the 2 screws, go inside the cabin and the brake light housing pops up.

4.) disconnect the bulb from the housing while inside the cabin (I had to do this with me two forefingers since the housing only pops up and inch or two).

5.) in the trunk remove the wire and bulb. (it's about 5 inches long. the wire from the connector to the bulb socket)

6.) reverse steps to install.

It is a pain and reqiuires a bit of time only because there isn't a lot of room to move around, but it beats taking it to the dealershio!