What would cause no power to the on-board diagnostic plug inside the vehicle
It is fused, I can't find a diagram for a '99
http://dodgeforum.com/forum/2nd-gen-ram-tech/302304-obd-fuse-blows-instantly-pcm-port-wont-read-radio-and-over-head-lights-wont-work.html ..Close as I can find. Often difficult to find anything on anything pre-2000 or so. It's a Ram forum but has some info that may or may not apply...Good Luck.
sometimes it is the cigarette lighter fuse.
Looking for a Used Durango in your area?
CarGurus has 23,191 nationwide Durango listings starting at $950.
Search Dodge Durango Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Dodge Durango Experts