Fritz330

I have a 2005 ES330 with Mark Lev and Nav. About a year ago I ordered a Grom unit to add a USB port to the system. Grom assured me it would work but it did not. Bottom line is with the CD unit disconnected the system would not switch to it. Grom tech support said it should but it would not. There is nothing wrong with the system, it functions normally with the CD unit connected. My question is, does anyone have it working with the above system? I would ask Grom but they seem to be clueless about the ML system.