Garmin G1000 Reference Manual page 190

SECTION 12 – ABNORMAL
OPERATION
Also, while the G1000 is in DR Mode, the autopilot will
not couple to GPS, and Terrain Proximity, TERRAIN-SVS,
and TAWS are disabled. Additionally, the accuracy of all
nearest information (airports, airspaces, and waypoints) is
questionable. Finally, airspace alerts continue to function,
but with degraded accuracy.
Garmin G1000 Cockpit Reference Guide for the Cessna Nav III 190-00384-09 Rev. A
12-4