engine light came on after driving during the day. weather turned colder also. what could cause this?

What is your question?

has not happened before. Motor does not sound any different. started right up and had no problems earlier when driving it. only time I have ever had problems was when the gas cap was not replaced properly. re adjusted cap this time and engine light did not go off. \

What makes this problem better or worse?

has only happened when gas cap was not on right. I readjusted the gas cap and it made no differents.

How long has your 2003 Toyota Tacoma had this problem?

just once today