As another datapoint, we just bought a new Clarity PHEV base model last week, and it ran great for the first 200 miles or so. After parking for about 30 minutes outside on a hot (~93F) day, the car started up with almost every diagnostic light on (similar to what others on this thread have reported, list below), even though it drove fine getting home.
Turning it off and on again did nothing the first 5 times (on the side of the road right after it happened, then four more times in our garage over a 24hr period at various hours of the day/temperatures). On the 6th try without having done anything different, the warning lights suddenly didn't come on (mid-afternoon, in the garage).
We have an appointment with our dealer/service center for this Wednesday -- will see what they say.
Thanks a lot for all the great information on this thread and forum.
-AK
List of lights/issues we saw:
1. Unable to switch between econ and sport mode
2. Emissions Systems Problem
3. Check engine light
4. Road Departure Mitigation System problem
5. Adaptive Cruise Control problem
6. Brake warning light (strangely, though, the electronic parking brake still works).
We did check to make sure the front-facing radar was not obstructed, but even if it was it doesn't seem to account for the inability to switch between econ/sport mode or the emissions/engine lights.