Thanks Len, this one won't work as I'm a 24vdc sytem and the Monaco is a twelve.
Go to
www.wabco-auto.com and click on product number. Enter 446 004 426 0 in the search box. Also, click on Publications and enter ABS and it will list four pages of ABS documentation. Have you check the resistance on the sensors? I'm not sure what resistance Wabco sensors are supposed to show.
You can try calling 1-800-535-5560 to see if you can get technical support from Wabco.
They are hall effect switches .. basically they operate when a magnetic change happens because a piece of metal crosses nearer to them and then is removed. I'm sure there's a resistance check but I've not found it -- I can however monitor the sensor leads using an oscilloscope and see the pulses go by when I rotate the appropriate wheel. Also, if it was a wheel sensor I'm supposed to be able to pull the trouble code out via the blink switch .. On my unit it never seems to get into that mode.
I've called them prior to posting this and they sent me a troubleshooting guide .. after that they basically wash their hands of me as they want an actual professional to look at it opposed to a garage hack like myself.

Doug, not many folks on this forum will have ABS knowledge - we all drive old clunkers

Yes, but there are (from all appearances) more do it / fix it yourself folks here which makes me feel more at home.
Your bus is five years newer than mine and it appears your ABS unit is connected to the data bus in your coach. It could be that the ABS light comes on if there is no communication over the data bus to the ABS controller.
I thought about this too, its possible the data line has failed somewhere. I asked Meritor-Wabco about it and they didn't know. I've been thinking that I should be able to use my scope to test this case .. Not sure what to look for, but if the patterns look the same as whats pouring out of the DDEC connector, then I can presume its getting the right signal down there. I will probably go try a few things with it in this area.
I have a Wabco 6S/6M 12v unit. Would this be of any interest to you?
I don't think I can use it. I'm a 24vdc 4S/4M system.
Thanks for the responses folks.