Check engine light

What is your question?

Everything going nicely, then I noticed car was running rough. Then I noticed the Check Engine Light was on. It had not been on before. Battery 3 months old. I purchased the car when it was 5 years old and I've always had work done & oil changes done by the dealer.

What makes this problem better or worse?

Don't know. Just happened.

How long has your 2000 Toyota Avalon had this problem?

One hour.