I received a pretty accurate diagnosis on another forum. There is a vacuum/pressure switch that is internal to the pump, and if it goes bad the pump will run until it is shut off by a limiter switch. If there was a vacuum leak that the pump was trying to compensate for, the door locks would not work right...and they do in this case.
The end result will be a trip to the dealer or a shop that I trust to either repair that pump or replace it. Maybe that's what the R stands for in R107 - repair / replace.
