The Canyon's trailer uses the old style round 4 pin female socket on the trailer with a jumper to the tow vehicle. I started Googling "round 4 pin wiring" to see what the standard is, and what a mess.  Websites you would think would have correct info contradict each other, so it's back to square one. I remember from the old days you basically wired a trailer to match the wiring spliced on the tow vehicle, but had forgotten how screwed up it was back then.
Looks like I'll be pin testing the trailer and making a jumper that'll match the flat 4 pin standard.