So I took delivery of my Volt on Thursday, and through part of my journey back to see family, I turned off the car. When I turned it back on, it said something to the effect of "Reduced Propulsion" and the check engine light came on too. With this message, the generator was always running, and it seemed that the "indirect" mechanical link between the generator and the wheels were all that were driving my car. Mountain mode could also no longer be enabled when this problem presented itself.
I tried powering on and off again, and got the problem to go away. It then happened later on in the trip too when I went to gas up.
It turns out that, with my Volt anyway, if after pressing the power button to turn the vehicle on, I continue to have my foot on the brake, some Voltec electronics diagnostic seems to fail. If I remove my foot from the brake immediately after pressing the power button, this problem doesn't occur.
If I had to take a stab at what's happening, perhaps there's some diagnostic test that monitors current draw or something to that effect, and the brake system is drawing too much during that test if I'm pushing on the brake, causing it to fail.
I've noticed from time to time a small pulsating on the brakes, and a small noise that occurs for about 3 or 4 seconds that seems to involve the brake/regen system when driving. I wonder if that's normal, and if it's that same behavior that's causing my propulsion message to appear.