Yeah, the monovalve and the aux water pump are two different circuits. The logic appears to be that if the PBU decides it needs a bit of heat, it turns on the aux water pump. It then pulses the monovalve to raise the heater core temperature to whatever point it mysteriously decides is appropriate. Aux water pump runs whether the monovalve is open or closed, so long as the PBU is in "heating" mode.

Give it a shot. It takes all of five minute to unplug the pump, no tools or disassembly required on my diesel. What's to lose?

- JimY