I know this post was last active in March, but I wanted to add a little information just in case someone does a search (this is the first result from a Google search "Mercedes GL changing parking/standing light" ). I also notice that this GL sub-forum isn't super active, so older post response doesn't seem that unusual.

The online owners manual (or paper manual) shows the front headlight assembly view very nicely on page 509. Page 511 shows the view from the rear. Page 509 covers the bulbs and their respective "type" numbers if you need to purchase. I had a burnt out parking/standing lamp per the manual terminology. Using the long handle needle nose pliers is a super good tip as noted. What I wanted to highlight is the need to really pull out on the bulb assembly after rotation of it counter-clockwise. I easily turned both bulbs, but what I didn't do was really pull back on them. I thought I was doing something wrong or possibly not turning them enough, but eventually I got more aggressive and sort of wiggled on them while pulling back and they came right out. One tip is that both sides are super close to some other sensor/plug type of thing and it made for a slightly odd time putting them back. You almost have to insert the bulb back in the "locked" position to get mostly seated, then turn counter-clockwise again to seat the assembly all the way again. Finally turning the assembly clockwise to lock it down. I replaced the blue tinted lights with some nice and bright LED ones.

 

I recently needed to change the parking/standing bulb on my 2011 GL550. The most difficult part as others have mentioned was rotating the bulb assembly counter-clockwise to unlock and remove it. As you can see in the attached pictures, I was able to use a long, flat head screw driver to rotate the bulb assembly counter-clockwise. There is a grey tab on the top of the bulb assembly that has a small gap just below it. I was able to insert the head of the screwdriver there and use it to rotate the assembly. Once rotated counter-clockwise, the assembly can either be pulled out by hand or with long pliers as previously discussed. Once the bulb is changed, it is easier to position the assembly in the "locked" position as mentioned by Nacho82 to bypass any obstructions and then return it to the unlocked position prior to fully reinserting and locking it using the screwdriver. Same method also worked for the driver's side. Hope this is helpful to someone. Definitely more complicated than it needs to be.

 

Thanks for the pics! Those helped me visualize everything. I used a long needle nose as suggested above, and was able to twist them about 45d clockwise and then wiggle them out. Worked pretty easily, with the drivers side being more difficult due to clearance issues. Had to reach the holder from above rather behind on that side, but it was fine.
Unfortunately the LEDs I had caused a fault, so didn't work out as intended. At least now I know it will work, just have to buy the correct LEDs to replace the incandescent bulbs. Thanks again!

 

Your talking about the bulb that looks YELLOW when on, beside the headlights, right?

 

This is the one I pulled out. It's yellow-ish in comparison to the headlights, but isn't actually a colored bulb of cover:

 

Yep, I'm replacing that today with a 5,000 kelvin bulb to match the headlights.

 

OMG guys - thank you for making this thread!!

my 08 GL450 passenager parking lamp went out and I was trippin out on how to replace it!

Love this forum!!!!

 

 

Yes, power cycle the vehicle (turn engine fully on and off) to reset the SAM. That will re-engage power back to the socket.

 

Get the long nose pliers.

Also, if you aren't careful, the bulb will pull out of its socket when you're removing it. This is not really an issue with incandescent bulbs, but is with most LED. One of my bulb housings now has two, count 'em, two, little LED bulbs caught in the space between the reflector and where the socket latches in. If you want to come over to my house, the bulbs are yours if you can get 'em out. You have to remove the headlight assembly, point it toward the sky, and shake up and down to get it out. You could shake the whole truck like that, but I'm not that strong.

I gave up on those parking lights. I'm just leaving the socket dangling inside the engine compartment with a bulb in it. Much easier to replace that way. They're mostly decorative anyway; when is the last time you wanted to navigate in a parking lot with your headlights off?

The front corner lights (marker lights?), however, serve a useful purpose by making the truck more visible from the side, and I'm going to install bright amber LEDs there.

If you want to comment on this thread, observe from the posts above that the details vary by year and headlight type. Mine is 2007 halogen.