I have of course read all the manuals and quite honest might not remember all the details over time. Good point to look at it again.
All I know (I have a SR22 G2 with the DFC90)
The TURN COORDINATOR only delivers data for comparison. A WORN OUT Turn Coordinator will make a "AHRS MISCOMP" message come up, meaning (in 90% of the cases) that the TC has to be overhauled. My PFD sometimes shows "AHRS MISCOMP" after 60 degree steepturns or other aggressive airwork. I will let the TC be overhauled soon.
Even with the "AHRS MISCOMP" message the A/P will stay on and fully functional if "Release 2" is installed. If the "AHRS MISCOMP" comes up on the ground, the A/P cannot be used and the aircraft must be handflown.
WIthout "Release 2" the A/P will go offline in flight – which is a very good reason (among others) to upgrade to R 2.
WIthout "Release 2" the A/P will go offline in flight
What does it do?
If the "AHRS MISCOMP" error message comes up then the Autopilot will stay ON and work properly if the reason is only the Turn Coordinator (which is only used for comparison) – if you have Release 2 of the A/P software. WITHOUT R2 the Autopilot will disconnect.
But if you have the "AHRS MISCOMP" message on the ground then you cannt engage the A/P and have to hand fly. Recycling the Avionics switch can sometimes help in this case.