Should have knocked wood when I posted (at least I think I did). Happened 2nd time last night, no apparent inciting events except that it was the first sub-freezing temperatures I have had two drive in for at least 6 weeks, maybe the entire winter. Came on in late afternoon, stayed on thru the end of my driving at 10 PM. Tried resetting both computers, hydraulic suspension all the way up then all the way down. Nothing changed. This morning, gone. Called Tesla as I was planning a 400 mile journey tonight and tomorrow, they told me no record of any suspension errors!
(PS with all the way up then down maneuver, instead of raising the car all 4 corners evenly as I think it has done before, it went all the way up front end first, then back end. Down was the same. Don't know if thats a helpful observation).