Question: I want to upgrade the head unit in my 04 accord ex. If I put in an aftermarket head unit, will the steering wheel controls be able to control the new unit?

If not, is there any kind of wiring harness or anything that I could get to make them work?

It would seem like a waste if they were not able to control anything.

 

There are interfaces that will allow you to use the steering wheel controls with an aftermarket HU. I'm pretty sure most brands with a hardwired remote jack are supported, which are most. Each interface supports a range of brands, but you need to get the correct one for your HU. I'm using a SWI-Jack with my alpine HU.