This was happenening to my car as well, and i will try to detail the fix and the reasons why it happens.
First of all you need to remove the Rocker Covers. They are the long plastic pieces that run from the back of the front wheel well to the front of the back wheels well and run under the door.
Once theose are out, jack up that side of the car slightly and crawl under there.
The issue (most likely) casing the flooding are called "weep plugs". The are little rubber insets that are pused into the bottom of the rocker panel area and you can just pop them out by hand. (and discard)
They are designed originaly to let water flow one way- out of the car. Yet as dirt and debris builds up over the years they got clogged up as the orifices in them as so small. Once they are clogged water cannot leak out from the bottom of the rockers and it fills to a point that it washes into the interior. This can cause wet carpets in both the front and rear floor wells and even a malfunction code (as you mentioned) of the seat belt wiring gets wet. (which will go away once things dry out)
SO over all its a simple fix, just remove both plastic rocker panels, pull out the 4 ( or so) rubber weep lugs on each side and that will allow all the ater to drain out correctly.
Keep in mind you my have another issue going on and my advice my not completely fix the issue, its just the best i could do based off your description and my own experiences. http://www.ls1gto.com/forums/showthr...light=flooding
here is a link to the thread.
Its a long read, but lots of good information and ideas in it.