Inspect the pass through wiring for the DCCD on the transmission (Passenger side just forward of the tail shaft housing. If that's good, then I would move on to checking resistance through the coil for the DCCD via that same wiring. Are you running a DCCDpro or MapDCCD? Yes, if the DCCD isn't wired correctly or if its fried it'll be open. What you can do is go to a parking lot and put in Manual and full lock, turn your steering wheel (left or right full lock) and give it some gas. For "auto" it can be a little more involved with detective work. The car should buck and scuff the tires. If it doesn't its not functioning correctly, more so, the center diff may need to be rebuilt (new clutch pack). Hope this helps.