My A/C controls are not working on my QX56. It is not the A/V unit. What else?

Hello, I would go back to the dealer and share with them that their diagnostic test did not yield a successful result, as you followed their guidance. The only thing that concerns me is that there is no way to know the quality and capability of the replacement A/V unit. Or, it could be that you replaced something other than the item they recommended. Any way you look at it, I'd consult them. Perhaps consider it a "recheck" of their testing. It's worth approaching and hopefully getting some assistance. There's simply nothing you can do without proper test equipment.