Updated: May 4, 2022
Here we go. A technical problem with me favorite racing simulator. As it happens, I tend to play with a small selection of cars, trying to improve my skills slowly, gradually, meticulously. One car, one track, and let the lap times go down. Over and over. Now and then, I do go for a little change of repertoire.
Several days ago, I noticed a weird bug in the Select Brand menu. Alongside the usual names and logos, there was an ugly missing-icon type of logo, and when I'd hover with a mouse over it, the text at the bottom of the screen would read unknown. Well, I decide to get rid of this problem, because my OCD demons demand it.
Problem: missing cars
I had issues with Assetto Corsa before. Corrupt game files and all that. So I decided to check the integrity of the game on Steam. No problem. I then went into the Steam install folder, and manually examined the different car models yonder. After all, whenever you get new cars - buy new DLC or whatnot - the car models are then stored in a specific directory on your system, and Assetto Corsa loads these vehicles into the Select Brand menu. I went through every single car listed, and I discovered that there were some incomplete models. The path you're looking for is then:
"Steam install path"\steamapps\common\assettocorsa\content\cars
Most cars had a pretty detailed directory tree - multiple sub-directories, image files, asset specifications, and such. However, there were several folders with only minimal content, just listing the "ui" sub-directory, and in one case, a car model directory was completely empty.
The fix to this problem, then, is to delete these broken cars from your installation directory. You don't really have to delete them, just move them away and place them in a backup folder of some sort. Then, load the game, and in the General settings, clear the Preview cache. Now, you should get a sane list of cars, without any silly icons.
In my case, all of the "broken" cars were stubs from one of the Dream Pack DLCs. I am not sure why the cars are missing (various Ferraris, as it happens), but maybe the DLC has not been packaged correctly, or some of its definition had changed over the years. Whatever the reason, I had my list cleaned.
And now that my OCD demons have been satisfied, I can rest. Or rather, not. Because the game beckons. It is time to race, sans cosmetic distractions. In general, the problem is harmless if annoying, but it does not negatively affect gameplay in any way. The only issue beside the visual niggle is that you may not be able to enjoy all of the cars you have purchased in a DLC somewhere. This might bother you, because money, then again, if you really want to up your skills, there's no need for more than 200-250 HP for a mighty race track experience.
If you see the unknown car brand icon in the list, then close the game, go through the Assetto Corsa install directory, and remove any partial or empty model folders. After that, clear the cache, and you should be good to go. Hopefully, this ought to help some of you. We're done. Vroom vroom.