I installed a round marine radio in my 2015 Base Slingshot, so I didn't use the factory radio harness, just an aftermarket connector to connect the radio power connector from inside the radio cubby area to my aftermarket radio. I don't know about the OEM sound system, but this Parts Diagram may be helpful - 2015 Polaris SLINGSHOT ALL OPTIONS (T15AAS/AAP) Electrical, Sound System T15aap All Options (49Slingshotsound14sling) | Cheap Cycle Parts.