I found a thread here
regarding this problem but it's rather old so I'll post a new thread instead of adding to that one in case anyone out there my have a similar problem.
Here's my sequence of events.
I replaced a battery and as soon as the new battery was connected, the air bag light came on. That really didn't make any sense as why that would trigger the air bag light. I had to go to the dealer for a $100 diagnosis that found broken wires in the driver's seat belt buckle. Apparently from what I've researched, this seems to be a common problem with the 2004 Sedona.
Anyway, the service advisor at the dealer quoted $200 to replace the buckle but said that if I was good with a soldering iron I might be able to repair it (they weren't allowed to do that), and the light should go out after a number of ignition cycles although the code would remain in the computer. (I found out later that wasn't good advice, or even accurate.) The service advisor also said that the code was probably in the computer although the air bag light wasn't previously on and that the loss of power by disconnecting the battery probably triggered the light when power was restored. In the absense of any other explanation, I have to assume that one is accurate.
The broken wires were clearly visible very close to the buckle and it was very easy to remove the buckle assembly from the vehicle. So I took it to my work bench and cracked open (carefully) the plastic buckle housing and easily soldered the wires, put it back together but the light stayed on. It wouldn't go out even after a couple of weeks. A mechanic friend (who doesn't have a code reader) suggested I try disconnecting the battery for a while to see if that would erase the code. I left the battery disconnected overnight and it didn't help.
I went back to the dealer to have the code erased and this time was told (by the mechanic, not the service advisor) that they wouldn't do that because the air bag system probably still wouldn't work after soldering the wires because adding the solder to the wires changes the resistance of the wires which the system measures. So there appears to be no choice but to go back to the dealer again to have the buckle assembly replaced and clear the code if I want the air bag system working.
If there are any mechanics familiar with air bag systems reading this, I'd appreciate if you could confirm if this was a correct explanation (just peace of mind!)
(To top it off, my safety inspection was due in the middle of all this. Fortunately the air bag light being on didn't fail the inspection as the inspection is concerned only with road safety, not passenger safety!)