Or it could be a fault in the BCM (body control module). Run a fault check using the AC buttons.
No, I don't remember how the sequence works, but here are the instructions:
"
To enter diagnostic mode:
Turn ignition "ON."
Depress the "OFF" and "WARMER" buttons on the Climate Control Center (CCC) simultaneously and hold until the segment check appears on the Instrument Panel Cluster (IPC)."
From
here.