kenwood dnx9980hd with nissan bose

Hello, I have 2007 Nissan Armada with Bose but no NAV. I installed a Kenwood DNX9980HD using Metra wiring harness. The Metra wiring harness has FR/FL/RR/RL RCA inputs. The SUV is equipped with a center channel and a sub. With those four connections made, the center channel appears to be playing. I presume the Bose amp that comes with the car is doing some signal processing. The sub on the other hand never plays. I am not sure if it is a separate amp or the same with the rest of the speakers. I configured the Kenwood receiver to ignore the sub preouts which turned off the XOver figuring it would send the low frequency signals through the other channels for the Bose amp to process. Still no sub sound :) There is an amp turn on wire which is hooked up properly. I had it improperly hooked up before and I got no sound out. Any thoughts or ideas on how to get the Bose sub to work? I would rather not replace the Bose sub/amp if I can help it. Just want a little a tad more bass without having to crank the volume.

Is there a High Pass Filter on the radio? Find it and turn it off. Plug the subwoofer output RCA instead of the rear, does the woofer work now? Does it work if you put the factory deck back in?

I'll put the factory one back and see how it goes. I don't think there is a high pass filter on the Kenwood dnx9980hd. I did plug the sub into the rear speakers and the rears played some of the low notes. But the sub itself never played.