Owners of other Kia, Hyundai or Genesis vehicles such as the Niro, Sportage, Sedona, Telluride, Sorento, Rio, Forte, Soul, K900, Cadenza, K5, Stinger, Tucson, Santa Fe, Kona, Palisade, Elantra, Sonata, Accent, Veloster, Ioniq, Nexo, Venue, G70, G80 and G90 may also find these DIY instructions to be helpful.

The compatible replacement light bulb part numbers are as follows: Brake # P21/5W, Rear Turn Signal 1156A (or 1156NA) and Rear Side Marker # 2825 (or W5W).

The tools needed to access and replace any of the bulbs include a 10mm socket with a 1/4" ratchet or a 10mm wrench, a small flat head screwdriver and a plastic pry bar tool.

The first two steps are to open the trunk lid and move to the side of the car with the burnt out tail light bulb.

Locate the rectangular shaped access cover attached to the carpeted fabric cargo area liner.

Gently pull the access cover out of the cargo area liner.

Set the access cover aside in a safe place.

Locate the white plastic electrical connector attached to the rear of the tail light housing.

Then loosen the four black metal nuts on the back side of the light housing by turning them in the counterclockwise direction with a 10mm socket and a 1/4" drive ratchet or a 10mm wrench.

Set the four nuts aside in a safe place.

The tail light housing is still held in place by a plastic peg or "spike" inserted into a grommet and also a slot attached to the button head of a plastic pop rivet on the front outer area of the assembly.

Gently try pulling the tail light housing straight off the rear of the vehicle.

If you have trouble loosening the friction fasteners, use a plastic pry bar tool to very carefully loosen the front outer edge of the housing.

Be very gentle to avoid cracking the delicate plastic lens on the light housing!

You can also try using a screwdriver or rubber mallet to gently tap on the threaded bolt ends attached to the back side of the housing to help loosen the friction fasteners.

Once the housing has been removed, set it down on a soft surface such as a towel or in the trunk.

Avoid placing the plastic lens on the ground or any rough surface to prevent from scratching it.

Use a flat head screwdriver to pry the white plastic electrical socket off the rear of the housing.

The orange plastic bulb socket located closer to the top of the housing contains the brake light bulb.

Rotate the bulb socket 1/4 turn in the counterclockwise direction before pulling it straight out of the housing.

Push a new number P21/5W light bulb straight into the socket and rotate it 1/4 turn in the clockwise direction to secure it into place.

If you would like to have brighter brake lights that will also last a lot longer before burning out like traditional incandescent light bulbs, install some compatible replacement P21/5W LED bulbs.

I left the brake light bulb socket out to leave more slack in the wiring for easier removal of the turn signal bulb socket.

Rotate the base of the bulb socket 1/4 turn in the counterclockwise direction before pulling it straight out of the housing.

Push a new number 1156A (or 1156NA "natural amber") light bulb down into the socket and rotate it 1/4 turn in the clockwise direction to secure it into place.

If you would like to have brighter and much longer lasting rear turn signal lights, install some compatible 1156A LED bulbs.

If you left the brake light bulb socket out, re-install it by turning it 1/4 turn in the clockwise direction.

Slide the white plastic electrical socket back on to its mounting post.

The small black plastic rear side marker bulb socket is located at the front outer edge of the housing.

Rotate the base of the bulb socket 1/4 turn in the counterclockwise direction before pulling it straight out of the housing.

Push a new miniature wedge base number 2825 light bulb straight into the socket.

If you would like to have brighter rear side marker lights, install some compatible replacement 2825 LED bulbs.

Re-install the bulb socket into the housing and rotate it 1/4 turn in the clockwise direction.

I had trouble rotating the small socket back into place, so I used a pair of pliers to re-install it.

Line up the slot on the back side of the housing with the white plastic pop rivet button head on the rear of the car.

Move to the inside of the cargo area.

Spin on the four nuts a few turns by hand in the clockwise direction to help prevent them from becoming cross threaded.

Tighten the four nuts with the 10mm socket and a 1/4" drive ratchet in the clockwise direction until they are snug.

You could also instead use a 10mm wrench if you have trouble getting your socket and ratchet in the tight spaces.

Try to avoid over tightening the nuts to prevent from cracking the plastic housing.

You should feel or hear the power plug "click" securely into place.

Line up the fabric access cover with the cargo area liner.

First, re-insert the tab on the rear edge into the opening. Then pop in the front side.

Rotate the black plastic knob 1/4 turn in the clockwise direction to secure the cover in place.

Check out my 2016-2020 Kia Optima Reverse & Parking Light Bulbs Replacement Guide if you need to change a burnt out reverse (back-up) or parking light bulb in the inner tail light housing attached to the trunk lid.

Be sure to write down the bulb change in your vehicle's service records.

Tip - If you installed an LED bulb for the side marker and it doesn't work, try removing the bulb from the socket, rotate it 180 degrees and push it back into the socket again. Some LED bulbs are "polarized" and will only work when the "+" positive and "-" negative electrical contacts are in the correct orientation.

Please check out all of my 2016-2020 Kia Optima DIY Repair & Maintenance Guides.