I know this has been discussed, and I thought I understood how to get this done. But apparently not.

I cannot get toms or hats coming out of AD2 to pan in the stereo field. All are on their own tracks in Sonar from AD2 in mono. All plugins in FX bins are stereo because it’s my understanding everything in the signal path has to be stereo in order to pan it. Interleave is engaged on all the (mono?) tracks. Still won’t pan. The L/R meter levels in the faders will reflect the pan position of the pan knob (say 30% right, or 17% left or whatever), but the actual sound won’t spread out in the stereo field. Am running all the toms to a stereo Tom bus then to master.

What am I doing wrong. Thanks in advance.

Try zeroing all track faders EXCEPT for the 4 toms and the hats, and check again.
 
If you have the AD stereo "Overhead", "Room", "Bus", or "Master" tracks active, you will get bleed from those into your stereo separation.

I found the AD2 track template provided in this article very helpful. 
 
Setting up a Drum Map for Addictive Drums 2 in SONAR
https://www.cakewalk.com/Support/Knowledge-Base/2007013364/Setting-up-a-Drum-Map-for-Addictive-Drums-2-in-SONAR
 

Track 15 is your MIDI track, which you can use to input the MIDI data for Addictive Drums 2. You can also insert any beat directly from Addictive Drums 2 onto track 15 by clicking the “Beats” tab in the upper-right corner of Addictive Drums 2, highlighting any beat and dragging it to Track 15.
 
The first track is a Master Track, which outputs all the sound from Addictive Drums 2 onto one stereo track. Most of the subsequent tracks are mono outputs for each individual drum from Addictive Drums 2, allowing you to process the audio from each drum kit piece individually. For convenience, the Overhead, Room, and Bus tracks are all formatted as stereo as well (as indicated by (ST) on the respective tracks. Note that processing in SONAR on any of these tracks will not affect how the AD2 Master (ST) track will sound; only processing within Addictive Drums 2 will affect the way this track sounds. This provides for lots of versatility, as you can use this track for things like parallel processing, having a dry track to compare to, or even having it muted altogether so you can monitor the individual kit pieces only.

abacab
Try zeroing all track faders EXCEPT for the 4 toms and the hats, and check again.
 
If you have the AD stereo "Overhead", "Room", "Bus", or "Master" tracks active, you will get bleed from those into your stereo separation.

By zeroing you presumably mean set to -INF, not zero 

Yup, close them down, as in no output.  I'm not an audio engineer.  Didn't mean to imply the 0dB unity gain.

Did some trouble-shooting, and don't know why, but the problem was caused by a buss in the signal chain. Toms were => "toms buss," => "Drum Sum" buss=> "all music buss" => master. Everything either interleaved or stereo busses. All plugins in the path stereo.
 
Hat was => "drum sum" buss => "all music buss" => master.
 
The problem was the stereo drum buss. Process of elimination routing directly from toms and hat to the master, and working backward through the busses. Adding the drum sum buss back into the mix revealed the problem. Eliminated in, created a new stereo buss set up exactly the same as the defective one, and now life is good. Panning works great. Who knows what ghost was in the bad buss machine... frustrating nonetheless. 
 
I can't figure out how to edit my original post and add SOLVED to the header... might help someone else trouble shoot a similar issue. Thanks again for weighing in! Onward...  
 
 

There should be an "EDIT" in the lower right dialog of your OP> 

Thanks Cactus... the time I've wasted looking in my account! :-)