I will use your pic to help you along,as you are looking at the picture,the carpet next to the transmission tunnel(where the black plastic footwell vent is),can be removed,a phillips screw and slowly pull away from the fire wall enough to see the heater case.
Once the heater case is visible,look on the sides where the case rests on the trans tunnel and you will see a foam black tube,that is you drain for the evap.Make sure it is attatched and going through the opening in the floor,if disconnected or falling apart do as the other gentlemen stated and replace them.
The check engine light was because the water corroded the socket on the o2 sensor,causing the check engine light.That was my experience,may be totally different for you.
The other test you could do,being that the carpet is out already,is to let a garden hose run along the cowl area and see if you have water entering the pass. compartment when you pass it around the windshield or cowl.
I hope this helps you!!!