MOTFSA is a 24 Hz clock (50% duty) used to clock data on MOTFSB. 
MOTFSA is generated by an open drain inside the MCM and a pullup to 5V inside the ECM. MOTFSB is generated by an open drain inside the MCM and a pullup to 5V inside the ECM. Cutting either wire sets CEL code. 

The ECM captures MOTFSB on each rising edge of MOTFSA. 
The MCM outputs MOTFSB on each falling edge of MOTFSA.

MOTFSB data has a 10 bit frame:
10 data bits
0 start
0 parity
0 stop

The MOTFSB line on a properly functioning IMA has only 4 unique frames:
'A' 1111111110
'B' 0000000000
'C' 1100110000
'D' 1111011000
'E' 1111011100
'F' 1100111100

Frames are broadcast continuously in the following order
(spaces added to show repeating pattern):
BABA BABA BABA BABA BDBD BCBC
Takes 10 seconds to repeat entire sequence (24 ten bit frames broadcast divided by 24 Hz).

Note every other frame is always 'B'.
('B' removed from the pattern to simplify):
AA AA AA AA DD CC AA AA AA AA DD CC
Looks like we're sending each packet twice.  
Looks like there's enough room to send up to five errors?

Does a continuous 'BABA' pattern cause IMA error codes?  If no error codes, then likely the 'BDBD' & 'BCBC' codes above indicate some error condition (or battery state of charge?).

...

Battery & BCM removed (MCM by itself, tons of errors, including P1644 P1581 P1648)
(spaces added to show repeating pattern):
FBFBEBEB FBFBEBEB FBFBEBEB, repeat

('B' removed from the pattern to simplify):
FF EE FF EE FF EE, repeat
