2008 Chevrolet Impala Electrical Problem: This may be simple, but you'll have to get the trunk open manually. Check the fuse block using the owners manual first, replacing any defective fuses. This may solve the problem as the wire loom for the taillights contains the trunk release circuit
If not then you can gain access to the trunk latch by releasing the split rear seat backs.
1. Pull up the driver's side seat cushion by pulling up on the cloth loop. It is located near the door side of the seat. Fish around in
the joint between the seat cushion and the seat back until you find it. Tip the seat cushion forward against the back of the driver's seat
2. Release the seat back using the loop located near the top of the back and tilt the seat back until flat against the seat cushion.
3. Repeat this action on the passaenger side rear seat.
4. Crawl into the trunk with a flashlight. Find the manual trunk release (a safety feature) which is a white plastic L-shaped handle. Pull the handle
and the trunk will open.
From behind the vehicle view the plastic trunk lip trim fascia. There are two plastic screws with a slot for a straight-bladed screwdriver (a small coin will also work), one on the right and the other on the left. Unscrew both of these screws (turn counterclockwise to loosen), remove the fascia and carefully lay it out of harm's way. The passenger-side taillight assembly is attached with three (3) plastic "nuts": one is the netting hook plus two (2) others. The lower one is near the inside to the fender and the upper one is accessed by reaching up into the inside top of the fender. Remove these three (3) nuts. Carefully pull the taillight assembly away from the fender. The three mounting studs will help support the unit. The unit wiring has a multi-plug which attaches to the taillight. There is a wire loom which goes to the driver's side through the bumper support bracket which has the left taillight and the trunk release wires inside it. Check for any corrosion or broken wires. Check the trunk release connection as well. All the multi-plug connectors has a water-tight lip-seal to prevent water from entering the plug. This seal has three ribs and is brown in color
while the multi-plug body is black.
As you didn't say how this happened, did you have a flat tire or go through a deep puddle or standing water? The wiring is reasonably well
protected as all wires are wrapped with electrical tape. If the fuses are intact did someone rear-end your car or have you hit a big pothole?
Which may have broken the filaments in the taillight/Stoplight/TurnSignal. By the way the bulbs are 3057 dual-filament clear available at most autoparts stores or Walmart's auto section.