Find the tail light bulb that is supposed to light up and check for voltage. If you get power, then your bulb is probably bad. If you get no power, then you are best checking whatever you spliced and finding a electrical wiring diagram.

 

Just curious. Did your 2005 come with OEM LED headlights.? If not. Converting from Halogen to LED can cause issues. (another topic, resistance).

From your post. It appears your problem occurred after your conversion. I would do a simple test. Re-install the
original bulbs. (you can leave them "hanging" to save time), and then turn on your head lights and check the rear tail lights.

If all good. As it should be. Then you can narrow down your fix, to something you did, when you converted to LED's.

Good luck.

 

My car came with OEM yellow (halogen?) lights. I'll try to plug in the old ones and see if the tails come back on.

If the brake lights work, that means the bulbs are good, right?
Could a bad fuse prevent the tail lights from working while not affecting the brake light control?

 

Just make sure the tail lights are getting power when they are supposed. Or just change all tail light bulbs. It's not impossible for both tail lights to stop working.

1. Get a multi-meter (I don't use test lights)
2. Check tail light bulbs
   1. Just because they look "good" does not mean they are good
3. Check for power when turning on the tail lights
   1. If there is no power, you will have to follow the circuit
   2. Get an electrical wiring diagram and trace the circuit and find component has power
4. Check the tail light bulbs again

Check the easy things before you start dismantling anything.

 

Found the issue. First thing I wanted to check before even going back behind the tail lights was the fuse, since it's the easiest thing. Lo and behold, this little bugger is fried to all hell. I'm not sure how that happened, but let this be a reminder... ALWAYS disconnect the NEGATIVE on your battery terminal when working on ANYTHING with wires in your car... Wires must have touched some time during my splice attempts with the halo LEDS and blown up this fuse.

Thank you guys for your swift responses and suggestions. I appreciate it a lot.

 

Always remove the negative battery connector or now your circuit.

 

So, I'm having the same problem, but I changed the fuse, and it keeps blowing what should I do?

 

Check the loom of wires inside the trunk by the left side trunk hinge. Open up that loom and look for broken or frayed wires that may be touching each other causing that fuse to blow.

Mike