Normally you shouldn't turn the ignition key anymore as soon as you have one of the (SRS) red plugs disconnected. You probably have turned the ignition key while you had the seat belt buckle disconnected...
Taking it to the dealer to get the code cleared is what you should do...It is not possible to clear SRS codes by disconnecting the battery.
N-E-1...anyone...It took me a while before I figured this one out, but I am getting there!
with a minor 600+k