Hello I will help you with your question,
The B1378 is for the side airbag and it usually is that the wiring under the seats has been pulled from objects being placed under the seat. If you have a 2.2 ohm resistor to insert in the harness side of the connector you can see if this is the airbag or the wiring.
I would also pull the connector off the airbag computer and inspect for corrosion, it may have been wet at some time.
The code is for high or low resistance so install 2.2 ohm resistors (the real dummy loads are better but who has those?) and be very careful not to damage the connectors.
If you can get the codes to clear then you can adjust the contact of the connectors as necessary to get a good contact and see if the side airbags themselves will clear when connected.
I have seen seats without the airbags inside so see if maybe they were removed leaving the connectors if you do not know the history of this vehicle.
Let me know how I can help