The wire on the harness is based on 12V and I'm not sure what RCJoyCon takes. The other way to interface is the 4 pin connector under the steering column. I can't remember if it's the 2 inside or 2 outside, but can look. 2 are for the backlights (12V when lights on, and ground) and the other 2 are 12V and the wire that goes to the harness. Find male and female connectors to go inline or clip the 12V and replace it with the RCJoyCon power side.