I checked Crutchfield.com, but since I don't know which Pioneer head unit you bought, I just selected one of the Pioneer models. Crutchfield also recommends an installation kit when you tell it what vehicle you drive, and will work with the head unit you select. For the one I selected there were two wiring harness options, one that provided support for the backup camera and one that did not.
So you might want to contact Pioneer about your head unit, and ask if they know of a wiring adapter that will allow you to use the built-in Honda backup camera.
So you might want to contact Pioneer about your head unit, and ask if they know of a wiring adapter that will allow you to use the built-in Honda backup camera.