2008 Tahoe Q6 stereo wire harness.

by Val
(Rockvale TN, USA)

I have a 2008 Tahoe Q6. I am putting small speakers facing out the back of the boat, next to the engine compartment air vent holes. The wire harness plug that the stereo plugs into appears to have both front and rear speaker wires. The speakers in the cabin are controlled by the front channel of the stereo. Does anyone know where the rear channel wires terminate in the wire harness? Or do I just need to run separate wires to the rear? I would prefer to use the existing wires if possible.
Thanks much for any response.
Val
Vcupples@gmail.com