Since today, whenever I load up a map, the D15 doesn't spawn and i'm left with a white screen (grid map). If I try to spawn other cars, nothing happens. I, R and J also do nothing. Is there any way to get this fixed without reinstalling the game?
Nope, unless the mods have changed any of the original game files. Also if you have customized one of the included input maps, I think those will get overwritten as well.
The updater will restore all original files to their default configurations. Any modifications you made to stock vehicles or maps would be reset. Whats happening to you sounds like you corrupted the D15 pickup, have you installed any mods to the default pickup folder or made any changes?
I haven't made any changes to the pickup but I have made changes to the engine files of the Covet and the Vanster. Regardless, I will reset my files.