[Twisted_Insane]

pawn Код:

if(sscanf(params, "ui", VehicleHealth)) return SendClientMessage(playerid, COLOR_GREEN, "/setvehiclehealth [Health]");

This should be ^:

pawn Код:

if(sscanf(params, "f", VehicleHealth)) return SendClientMessage(playerid, COLOR_GREEN, "/setvehiclehealth [Health]");

The vehiclehealth gotta be a float, so why should you use "ui"? (integers)? The 'f' - specifier is for a float, that's also what the guys above me told you.