It appears you are correct, DAS is apparently stand-alone in the 1998 W140. Got a call from my cousin last night, he found the STAR wiring diagrams on the laptop and located the source power fuse for the DAS module. It was either blown or had a mechanical failure and was not supplying power and he reports the car is now fixed. I'm sure he'll chime in when he gets the time and fill us in on the details.