Ok, so I got a used FCIM off eBay, same part number JL3T-18E245-UCE but listed as one for model years 2019-2020 (I have an early model 2018). I noticed the actual circuit board of the HVAC section (lower board) had number P255 on it, but also additional marking MY18. The MY18 was not on my original board.
So I hooked it all up and BINGO, no passenger airbag light anymore!!!
But testing everything I noticed the little light for the “AUTO” HVAC did not light up. The functions all seemed to work ok, just no light.
Do the 2019-2020 not have the light on the “AUTO” button to show on/off???
So I pulled everything back out, disengaged the ribbon cables connecting the 2 boards and swapped out my old lower board (HVAC) with the new upper board. Reinstalled and now everything works perfectly.