HOW DO I CHANGE TAIL LIGHT LENS IN 04 SONATA AND WHAT TOOLS DO I NEED

Don't know if this will work on your 04 Santa Fe or not. This YouTube video shows how to remove the connector on a 06 Sonata. May offer an idea as to how its done.
https://youtu.be/VIs1ZKljeAk

How Do You Change Tail Light Bulb
Remove the wiring harness from the tail light lens assembly. Disconnect tail light bulb from the wiring harness socket. Reconnect the wiring harness to the tail light lens assembly. To confirm proper installation of the new tail light bulb, place the key in the on position.
IT IS VERY SIMPLE OR GO TO AUTOZONE AND HAVE THEM CHANGE IT OUT FOR YOU AND WATCH THEM ONCE. GOOD LUCK.

Then you need someone who can,like a repair shop

It can be faulty tail light bulb or its issue with tail light control switch or its wiring's are short.

Check the voltage at fuse slot of tail light.Do you receive 12 volt there.If not,then it says tail light switch is not receiving power supply.


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There are few help links related to your problem.I suggest you refer the list and check the help links.Click the link below:-----
1994 Toyota Camry: Bypass Tail light Relay Circuit? http://whatisbyme.blogspot.in/2012/04/1994-toyota-camry-bypass-tail-light.html

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2008 Toyota RAV4: Replace Tail light Lens Cover?

http://technoanswers.blogspot.in/2012/04/2008-toyota-rav4-replace-tail-light.html
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2003 Chevrolet S10 Tail light Fuse http://schematicsdiagram.blogspot.com/2012/11/2003-chevrolet-s10-tail-light-fuse.html
--------- Chevrolet Parking light and Tail lamp light Wiring diagram http://schematicsdiagram.blogspot.com/2012/11/chevrolet-parking-light-and-tail-lamp.html
---------- Car Tail Lights Not Working?

http://schematicsdiagram.blogspot.com/2011/12/car-tail-lights-not-working.html

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Turn Signal Not working http://technoanswers.blogspot.com/2012/11/turn-signal-not-working.html
---------- Right turn signal not working on Pontiac Car?

http://schematicsdiagram.blogspot.com/2011/12/right-turn-signal-not-working-on.html

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Only one side indicator light working on car?

http://schematicsdiagram.blogspot.com/2011/12/only-one-side-indicator-light-working.html

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Turn signals not working on 1987 Jeep Wagoneer? http://schematicsdiagram.blogspot.com/2011/12/turn-signals-not-working-on-1987-jeep.html

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SOLVE YOUR 4 WAY FLASHER RELATED PROBLEMS HERE
http://repairhelpcenter.blogspot.com/2012/11/4-way-flasherturn-signal-flashersignal.html

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Thesedetails will help.
Thanks.

I assume you're asking if only the lens can be replaced. I'm afraid not. The tail lamps can only be acquired as complete assemblies. You will see what I mean when you remove the assembly and examine it. There are three (3) to four (4) 10mm nuts holding the assembly in place and can be accessed from inside the trunk. You'll need/want to use a deep-well 10mm socket.

Entire assembly must be changed.

I think it is the same as a '04 maxima. Open the trunk, from the inside remove the side trunk liner (by removing the plastic tabs the liner can be pulled back). Once the liner is pulled back you will need to remove two nuts which secure the tail light in place. Once the two nuts are removed you can start pulling the whole tail light assembly out. There are two other tabs that secure the tail light in place which may give you some resistance but the light should come out without too much force once the two nuts are removed.
Once the tail light is out you can change whatever bulbs you need to.

Open hatch and on inside of body where the lens is are two horizontal screws going into the lens, remove them and pull the lens towards the back of the vehicle carefully. Good luck

Access to the brake light bulb is through the tail light lens. First, remove the tail light lens by removing the single star shaped screw that secures the lens. You do not need a special screwdriver or bit: a regular flathead screwdriver will work fine.

Get in the trunk, take loose the screws, lift the lens holder, change the bulb. Unfortunately, it's not as easy as it sounds. The hole for the lamp position is offset about 4-5 inches. You cannot get to the bulb to remove it without taking loose the lens holder. You have to remove 2 screws to do that, one of which is hidden by a piece of foam tape.
Also it is impossible to remove the lens holder without slipping a finger underneath to turn the bulb holder. I had to cut off a portion of the bulb holder to slip the lens back in. I left the screws out, as it is impossible to put them back after removal. No wonder the dealer wants $50 to change the bulb-it took me about 45 minutes.