My rear passenger side marker light died. At first I thought, I'll just pull the side trunk liner out and I'd have access to the light. But I realized that was a dead end - nothing but sheet metal behind the liner. I found a thread entitled "Help: How Do You Remove Rear Bumper Lights?" that it somewhat related. There was a debate about whether you had to remove the bumper. What worked for me was to remove the bumper part way. Here's what I did:
(1) Pop trunk and remove two bolts securing the passenger side tail light assembly. Use a cloth wrapped screw driver to gently pry the assembly off the two aft facing pins it rests on.
(2) Remove fender liner aft bottom section so you can get to the upper forward bumper bolt. There are 4 hex bolts holding on the liner. You don't need to take the bumper leading edge trim off (2 phillips head screws).
(3) Remove upper forward bumper bolt and the first (side) and second (rear) bottom plastic pins that secure the bottom of the bumper.
(4) Gently pry the bumper off the square peg just forward of the tail light mounting area.
(5) Pop the bumper off the plastic ball socket which is about 6" further forward.
(6) Now reach behind the bumper from the front and quarter turn the connector.
(7) Pull the tape of the harness inside the bumper so you can get enough play to drop the connector below the bumper where you can see it.
(8) Install the new bulb, turn on the lights and make sure it works. Then reassemble.

If you can reach the connector and turn it without removing the bumper, you're a better man/woman than I. And I'm a pretty skinny guy!

 

OK. I hit the photo limit, but there is more to show. The square pin and the ball fitting are shown below, among other shots.

You can see my skinny arm reaching aft from the front edge of the bumper!

Also, I provided a shot of the bulb so you can see what the prize is at the end of all this work. My bulb was brown and the connector was filthy. But I'll address that in a separate post.

 

As noted in the previous post, the marker light was brown and the connector was filthy. I cleaned the connector the best I could, but when I installed the new bulb (194), it had an intermittent connection. The metal prongs were splayed within the connector. I used an awl to push them closer together (with the elbow fitting removed and unpowered!). This only helped a little bit.

I cut some small strips of plastic from an old credit card. I used tweezers to insert these behind each of the 4 prongs to try to squeeze them together (see white edges in photo).

This made for a tighter fit, but the bulb could still shift in and out of socket a hair. When it shifted back the light would go out. So I dropped a couple more shims down between the prongs. This prevented the bulb from shifting too far back.

Now I probably could have just gone to the Lexus dealer and got a new elbow connector, but I'm a cheapskate. At least now I know how to get to this bulb again when my jury rigged spacers fail!

 

I easily did my front ones and i struggled forever with the back ones, looks like i was tryign the hardest way possible.

 

I can totally relate. In this case I had the benefit of an earlier thread on the topic and I had already pulled the front bumper and fender liner to replace a headlight ECU last January. I was amazed how few bolts/buttons held it on!

The irony of this is that I took the car to VA annual safety inspection yesterday. The side marker was fine, but the front and rear parking lights were out! I told the mechanic I had just checked all the lights, He was a good sport and tested them again, they all worked, and he passed it. When he pulled the car out of the garage, the front one went out again. So he taps the highlight assembly and it comes back on!

I pulled out the front connector this morning. It was clean (unlike the rear side marker connector), but the bulb was a little loose. I sprayed some contact cleaner into the connector, and it seems to stay lit, but I'm gonna keep an eye on.