I can't remember if D08 is still connected to the chip but originally that pin was intended to be a 'Start Serial Data' input flag to the MCU 1 chip. The high/low state of D08 would make $0881 bit 4 = 1/0.
The MCU 1 chip is the hardware that latches conditions like A/C turned on (bit 5), tranny 3rd gear switch closed (bit 6), and/or trans in P/N (bit 7).