Did the obd scan, nothing came up. Do you remember what sensor was faulty? \Thanks for the reply guys. I will definitely clean the IAC valve

Hi everyone,hoping for some input for my wifes 2000 S40. While driving, the car will randomly downshift without warning. She usually has to pull over and shut of the car for about 5 minutes. She than can continue on her way. She has said, sometimes, when she turns the car off for the 5 minutes and r...