I did exactly as the Arnold documentation states. Checked on the Merge AOV in the driver node. Z pass works just fine in CPU render mode. It renders white, but playing with the exposure I can bring back the Z depth information. But, in GPU, it renders black. If I mess with the exposure in the Arnold ReviewView window, or in Photoshop it does not show any Z depth information when using GPU.
Anybody know how to get this to work in GPU. I read the documentation, it says Z AOV is supported in GPU mode.