Check engine light flashing

What is your question?

Driving up a hill and my car lost a little power and my check engine light start flashing. I changed spark plugs. It was driving fine with power. I drove up a hill 2day and same result. Light stop flashing when I got on level ground. And to add it has been over 100 degrees outside

What makes this problem better or worse?

Only been happening since it been hot outside

How long has your 2009 Toyota Camry had this problem?

2 weeks