Yikes-- somehow the DAC switch was engaged while driving down the highway. I only noticed because the light started to flash on the dashboard. There was not change in how the car was driving, so I suspect that the DAC can only be engaged in 4LO. The truck seems no worse for the mistake. Anyone have any thoughts about any negative consequences? Along the same lines-- what would happen if someone hit the 4LO swith or the differential switch. Like the DAC, they shouldn't engage, but what would happen?