I'm sure there are several options for where to add LEDs so that the hupholders are illuminated. I thought through the pros and cons but eventually decided to remove the cup holders and add them inside the actual cup holder. The hardest part of the project is figuring a way for the wires that power the LEDs to slide in and out with the cup holder.
Step 1: Remove trim and cupholders:
I used an ID card (Costco Card) and applied light pressure back and forth across the trim piece. As you can see, there are two posts in the center and these slide out rather easily. The clips on each end hold a little stronger. I would recommend against pulling out from the center because the trim piece gets pretty slim along the cup holder. Instead, use the card on the end and on the vertical side at each end. Just apply some pressure and work it out. After that, it's just a matter of removing the two screws on each cup holder. Here is a diagram and a photo of the actual trim piece.
Step 2: Opening Cupholders:
The cupholders have tabs on each side. Using your fingers or an ID Card / small screwdriver, open each cup holder. There is a slight difference between driver's and passenger's side coil springs you need to be aware of. The coil spring for the passenger side cup holder is mounted to the lid. So when you separate the two sides the cup holder may shoot forward (nothing drastic). I recommend that you extend the cupholder to relieve most of the spring tension, then grasp both pieces securely (or make sure it has a soft place to land).
The driver's side coil spring is mounted to the bottom so opening the top is worry free.
Step 3: LED Placement:
I ordered 3mm pre-wired LEDs from Oznium.com
in orange. They match the existing ambient lighting perfectly. The picture below shows where I placed my LEDs. There may be other options, just plan carefully and test before glueing. Use a 9v battery with alligator clips to test the lights in the car and make sure nothing is shining in your eyes. Also, you can use 600 grit sandpaper to diffuse the light from the LED so it glows instead of shines on a single spot.
The passenger side LED placement required that I drill small holes in some of the internal plastic fins for the wires to pass. To do this, I used a very small screwdriver. I heated the screwdriver until is was glowing red then carefully melted my way through while twisting to make a round hole. Use care and work slowly and it will come out smooth.
Step 4: Fabrication for the LED wires to slide with cup holder:
This is probably the most difficult part. Because the LED is glued to the sliding portion of the cupholder you have to allow for this wire movement. To do this, I used the straw from a spray bottle to give me something with the flexibility yet rigidity I needed. I tried multiple straws until I found one with just enough inner diameter to fit two wires. With the cup holder in the closed position, I drilled a hole through the back of the cupholder case and into the internal space where my wire connections were made. I made the hole as small as possible, then glued the straw in place, with the two wires passing through it. You will need to do some trial and error to make sure you have clearance behind the cup holder for the straw when it is mounted back in the car. Test, test, test before glueing into place.
Step 4: Wiring:
After you've tested everything it's time to assemble and wire. There's no mistery to the wiring. I used 22 guage wire for all connections. I left plenty of excess wire so there was room for movement. I had an existing fuse tap for a radar dectector so I just tapped into this.
The pictures aren't great because its hard to get pics of LEDs in the dark. However, the LEDs cast a nice glow over the cup holder without shining in your eyes.
The cost for this project is relatively low. The LEDs cost about $10 with shipping (I ordered extra) and the wire and connectors cost about another $15. Also, there's very little risk. I could reverse the whole project and never know anything was modified since it's all internal. Besides, if you muff-up something, I think the cupholders are $35 each to replace.