Because you are asking a question that has already been answered, yet you did not see it.
Stock is stock, and aftermarket is aftermarket. They do not play well with each other. If you want to not "mod" anything, stay stock. If you want something better, get the wiring harness and adapters you need, and plug-and-play with aftermarket.
Stock is stock, and aftermarket is aftermarket. They do not play well with each other. If you want to not "mod" anything, stay stock. If you want something better, get the wiring harness and adapters you need, and plug-and-play with aftermarket.