The battery came back from the shop today - looks brand new and a full charge fills most of the bar graph on the dash - best it's been in 3 years. First attempt to move briefly showed a 209. Sprayed the controller plug-ins with contact cleaner and re-seated them. Brakes released and truck is now working fine with no codes.

I recalibrated the accelerator and steering - this time voltages displayed on the dash were normal. Thanks again for your help. The Yale is back in service just in time.