'96 Miata, w/ OBD II

CEL has been coming on, then after a few drives, going off.  This has been
repeating itself for a few weeks now.

Each time I check for a code, the scanner returns P1794.  The documentation
that came with the code reader states "Manufacturer Specific Code".
Searches on the internet suggest, "Honda/Acura auto trans code".  I can
clear the code, but it comes back in short order.

Sometimes, not every time, when the CEL has not been on, I'll start the car
and find that the radio will not turn on for a few minutes -- a glance at
the dash shows the CEL on again.  Don't know if the two are related.

Can anyone tell me why I'm getting this code on a 5 speed equipped Miata?

Thanks!