Finally got the issue resolved. Turned out to be the entire wiring harness for the airbag system. They replaced it from "battery to bag". They installed a 'test harness' and I drove it around for two weeks. Then they ordered the new harness and it took a couple of days to install (they have to rip out the seat and almost all the interior panels). Thankfully under warranty and Jim Click Ford in Tucson was excellent with arranging a rental car. The regional Ford folks (Brad) was also a pleasure to work with. Here's a tip... don't be impatient with them. If they're calling in engineers, odds are it won't be done that afternoon.