Hose Disconnect Causes Possible Service Engine Soon light to come on

My husband was changing the air filter in our 2001 Chevy Venture and one of the emmissions hoses got disconnected. The check engine soon light is now on and he cannot find where to reconnect the hose. Can anyone help? Thanks. :p

Which hose is it? There is one hard plastic one going into the rubber duct at the throttle body which is simply an oil breather tube, which won't set the light.
There is the PCV hose going into the valve cover in front, which will cause a high idle and ses light.
There is a plastic black tube with a green fitting in back of the fuel lines by the master cylinder which attaches to the EVAP system, this will also cause an ses light.
Best to describe the hose as well as you can, I can probably help then.

Check vacuum hose that plugs into front of transmission just below air cleaner housing. I had this same problem when I changed my air filter and it took me several weeks to figure out that this vacuum hose had been accidentally pulled loose. The SES light would stay on and the transmission would shift pretty hard between gears. Hope this helps.