OBD2 Code, no prefix.

Hiya Jeepies,
Got an odd, and thankfully, intermittent problem with my 97JGC.
At highway speed, and at operating temp, it will begin to run rough, I’ll get a flashing check engine light and an odd, almost sweet smell as the problem continues. It’ll do it for a minute, and then go back to running normally.
When I do the switch trick to pull a code, it’ll flash a “12”. No prefix, just a 12.
Anyone have any idea what a 12 code could stand for?
I’m worried that one of these times it’s going to start running like that and not quit it on it’s own. I’d like to get it figured out before that...

Thanks in advance!

Code 12 is usually just indicating the battery was disconnected recently.

Turns out the culprit is a misfire on #5 cylinder, came up when my mechanic put his scanner on it.
Scheduled an ignition module change out for next Saturday...
We’ll see if that takes care of it.