I do not have access to a schematic, but you could find that on an online service manual service such as AllDataDIY, or you could find the actual service manual if someone has uploaded it online for free-use.
Mine quit working after the warranty engine change, I have yet to discover why mine stopped working. I know this is specific to the circuit of the horn button as I can still activate the horn via the panic button.
"Why would I want to profess my feelings for some 3D girl?" - Tomoya Aki from the anime Saekano