The PFD Field Level Troubleshooting Guide P/N 600-00722-000 Rev 00  references ADAHRS Miscompare for a Dual PFD configuration. If you have a single PFD and a DFC90; refer to the DFC90 Install Manual 600-00251-000 Rev: 09 or later. 
Single PFD with a DFC90: Check the blind turn coordinator, the DFC90 is using this to compare.