Just installed a new Pioneer MVH-620BS head unit with the 70-7551 aftermarket wire harness in my 2006 G35 sedan (w/ the Bose system) if that matters. Everything hooks up correctly and looks fine but the volume is just extremely quiet until you reach around 35-40 on the head unit which maxes out at 62 and still isn't necessarily loud. I don't think it's a power issue because I connected the ground wires to the body itself instead of through the wire harness but I'm still experiencing the volume problem. It may be a setting on the head unit itself that I need to find or I may just need to try another wire harness and start over. need help if anyone knows anything or has ran into the same issue

 

Did you hit the "reset" button after installing. I'd try that first. Just to the left of the Aux input jack and you need a pen or something small to press it.

 

Moving this thread to the AV subforum.

 

You used the wrong harness to connect to the Bose system. You need to use the PAC ROEM-NIS2 adapter to maintain volume when connecting an aftermarket HU to the BOSE amp.

https://www.crutchfield.ca/S-MN8ocSg...Interface.html

 

He is correct . Bose does not use standard ohm speakers (2 ohm, 4 ohm, 8 ohm ) so when you connect an aftermarket head unit to a Bose setup it doesn't match and that's why it quiet. This is why if you re-install the original head unit you'll notice it's louder .

 

It's not the ohms. The bose radio and amplifier are set up for a differential-balanced signal, so a standard signal being fed into the bose amp is sort of like noise canceling headphones, but the noise it's cutting is the audio signal itself.