The legend shows this:

The wiring diagram shows this:

Are these the same symbol? If not, what is that symbol next to C4? There is no other symbol in the legend that looks remotely close to this symbol besides the one in the first image.

 

bulkhead connector C4 is shown. the chevron symbol also means connector male and female sides indicated. bulkhead connectors pass through a bulkhead, or wall or such. non bulkhead connectors have the chevron symbol only, but if it is through a bulk head you get the additional symbol for bulkhead.

good luck