Garmin G1000 Cockpit Reference Manual page 112

SECTION 12 – ANNUNCIATIONS
& ALERTS
Display is not receiving altitude input from the air data computer.
Display is not receiving vertical speed input from the air data computer.
Display is not receiving valid heading input from AHRS.
GPS information is either not present or is invalid for navigation use.
Note that AHRS utilizes GPS inputs during normal operation. AHRS opera-
tion may be degraded if GPS signals are not present (see POH).
Display is not receiving valid transponder information.
A red 'X' through any other display field, such as engine instrumentation
Other Various Red X Indications
fields, indicates that the field is not receiving valid data.
Garmin G1000 Cockpit Reference Guide for the Beechcraft A36/G36
12-8