Chrysler Repair: 99 mini-van shifting out of D

Question
1999 Dodge Grand Caravan 3.3L 4speed 219K

It has happened a few times that while driving, the van will disengage from D. At this moment, the tachometer shows the rpm but both coolant temperature and speedometer needles dive to zero (of course both are not correct as the engine is hot and van is still driving on road at some speed more than zero). Pressing gas will sound like the transmission is in N where it is showing as in D. Usually, I slow down, pull over and as soon as I put the gear selector in N, all needles go back to showing normal operation. I restart the engine and then go on like nothing happened until it happens again.

What to check first?

Thanks

Answer
Hi Shafique,
The only common connection between the trans range selection, the engine temp sensor, and the speedometer would be likely the digital data bus which is a shared communication system connecting many different operation modules. I would try a fault code readout using a plug-in code reader as you have done in the past. Let me know if you get any codes.
Roland