Thread: P0440 ses code. Really need help!!

I need some help with this code. For the last week and a half, my gas mileage has slowly been dropping and today, the ses light came on. I took it to autozone for the diagnostic and i got the 0440 error. I popped the hood and with some carb cleaner, sprayed down the hoses to see if i had any leaks. I couldn't hear or see any. I'm very confused and i could really use some help and advice. Thank you.

defintition of the code would help most of us out here cuz we dont memorize them!