Update on Engine warning light. Well, I went out to start the X in -32c weather this morning, and it started without a problem, AND the Engine Warning Light was now off (after being on for 2 days).

I went to the dealership anyway and asked them what I should do, and they said no need to bring car in now, as long as car was running properly (which is was and is).

We have made a note and put it down to the extremely cold temps this weekend.

I will update if there is anything new to add.