DTC 31 is B1000, not B1100, but you're right, that's the center airbag sensor assembly. I don't think there is a B1100. I suppose that's what you are also calling the airbag control module, it's the one under the front of the center console?
Did you reset the codes and have them come back? If not, do that. It's not enough to just disconnect the battery. If you can't get the body shop to do it for you, there is a procedure but it's tedious. Let me know.
If the code comes back, sorry, your new assembly is also bad. To make sure, swap it out with another Taco's to make sure.
EDIT I see you have a Tundra. Wrong forum, try the Tundra forum. I think my comments will generally apply, but I could have some details wrong. I think there IS a B1100 for the Tundra, it is the same, I think in the same place as the B1000 I described for the Taco.
You could also check for power in your connector. I think there should be +V in the top two left pins of the center connector relative to ground.
I don't have a Tundra though.