Its very simple and there may not be much demand for this as I don't think too many 204s had this option but mine is a 2015 and does have this annoying option.
I didn't find much information on disconnecting this for face-lift 204s where the star stays lit while driving which I hate, it was all for earlier cars where the benz star in the grill could just be rotated and popped out, which mine cannot, or for earlier versions where the star did NOT stay illuminated while driving, which seems like a better option to me. I also looked through a lot of 204 fuse box diagrams and didn't find a dedicated fuse to pull out to disable just the illuminated star.
While I was looking at space for a catch can I decided to pop off the cover over the radiator support and handle the illuminated star problem.
The cover pops off with no tools, you just rotate the pushpin in the center to disengage it, unhook the hose from the tab on the passenger side rear of the cover, unhook the cable from the tab on the drivers side rear of the cover, press down on both tabs to unhooked them from under the support and slide the cover off.
With the cover off there is plenty of room to reach down behind the grill star. At the bottom of it is an obvious 2 wire electrical connector. Just push down on the safety on the star side of the connector to release the connector and pull apart to disconnect it. Here it is already disconnected.
since the connector ends are in a location where they might get wet, I packed both sides of the connector with dielectric paste then wrapped them in electrical tape. The connector on the star side is very short and can just be pushed underneath out of sight without any chance of it dangling or moving around. The electrical harness side connector I ziptied in the aluminum channel using an existing empty hole.
That's it. Re-install cover and never be bothered by the cheesy light up benz star again. (When it showed up lighted in the nightime track photos from the photographer at Palm Beach Raceway is when it really bothered me)
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
