when I started my car in 11' temps the engine light went on, why?

What is your question?

I started my car on a 11 degree day, the engine made a winning noise so I shut it off. When I restarted the car the engine light came on and I tried the gas cap trick but engine light is still on. Car runs fine, can't find any leaks. Had knock sensor replaced a month before light went on, maybe a defected knock sensor? Been driving car for 4 month with light on and no visible signs of trouble?

What makes this problem better or worse?

cold starts, car runs fine after warms up

How long has your 2001 Subaru Outback had this problem?

few months