Figures. I never bothered to check the Haynes manual, which details just how to diagnose and read seat codes. For posterity's sake, I'll detail the procedure for reading poser seat fault codes as it's a bit more complicated than engine codes.
1. Insert lest lead into socket 6 of diagnostic socket B.
2. Press any button on the seat control panel, keeping it pressed down while at the same time turning the ignition on to pos. II. Continue to hold the button down for about another second.
3. Then go to the engine compartment and press the button on the diagnostic unit.
Procedure must be done all within 30 seconds.

I had 1-2-1, "Signal position sensor, motor 2, absent or faulty" and 3-3-2, "Lead disconnected, motor 2." These were both from the previous days troubleshooting. After clearing the codes and fiddling with the seat some more, no codes returned...

I ended up driving the seatback up by inserting the cable into the opposite end of the motor, so effectively down was up. After a bit of reassembly and fiddling with it some more I found that the memory buttons would bring the seatback up, something I hadn't observed previously. All three settings brought it past vertical, leaning towards the dash. I decided to cut my losses and button it back up. It still won't move with the switch, but Memory setting 3 is now reserved just for the purpose of raising the seatback. Still have full range of motion and it works great otherwise.

Back to driving the 850 and fixing the 240.

Thanks,
Will
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850 / Mini