Search in profile fields using sdk

Hello, everyone
at first, Happy new year

I wanna search for vehicles by profile field for specific field_name like "year" or "registeration_plate",
This is not working, when i wrote the doc, i understood that i can set  like this:
propName : "rel_profilefield_name",
propValueMask : "registration_plate:value",

this is my code :

        SearchSpec searchSpec = new SearchSpec();
        searchSpec.setItemsType(Item.ItemType.avl_unit);
        searchSpec.setPropName("rel_profilefield_name"); //sys_name
        searchSpec.setPropValueMask("registration_plate:"+v.trim());
        searchSpec.setSortType("rel_profilefield_name");
        searchSpec.setPropType("profilefield");

But this not going to work, what is the problem please?

thanks