jauh,
it is known and agreed that ISIS consists of a gyro system
among other sub-systems. That's why it is sorted at 34-22 Directional Gyro & Indication. But there is an Air Data part as well. And an AP interconnect. And GPS, ....
To me, the actual message does not indicate that the
gyro of ISIS is broken, which in turn means that its Attitude Indicator would be lost.
The ATA code just tells that there is some problem with ISIS, but not which one. Could have been the ISIS display or the air probe inlet clogged or... except we can decipher
which I am not sure about, hence my questions which I am sharing with PJ2.
Unfortunately my next access to AMM / TSM has to wait until Monday. And yes, I do read almost every single post, including yours. :-)