Sorry to reply to my own post...
It was a fuse. I just checked them all until I found a failed one. After replacing it, went back and they got a 402 - EGR Flow Excessive. Surely this fuse couldn't be for the whole PCM - it wouldn't run at all would it?
Anyway, the EGR valve checks OK. I took it off, cleaned it and tested it with a vacuum pump. When closed, it seems to seal well.
I hooked a vacuum gauge to the EGR side of the vacuum solenoid. No vacuum at idle, vacuum at mid throttle, none at higher throttle (this is with the van in Park and warm).
All of this seems to be correct. Am I missing something?
TIA, Wallace