GMC 2001 Sierra 1500 Pickup Owner's Manual page 183

When the transmission enters the protection mode you
may notice a change in the transmission shifting
patterns. When the transmission fluid temperature
returns to normal, the display will turn off and the
transmission shifting patterns will return to normal.
NOTICE:
If you keep driving your vehicle with the
transmission TRANS FLUID HOT message
displayed, you can damage the transmission.
This could lead to costly repairs that may not be
covered under your warranty.
2-100
The following situations can cause the transmission to
operate at higher temperatures:
D
Towing a trailer
D
Hot outside air temperatures
D
Hauling a large or heavy load
D
Low transmission fluid level
D
High transmission fluid level
D
Restricted air flow to the radiator and the auxiliary
transmission oil cooler (if equipped).
A temporary solution to hotter transmission operating
temperatures may be to let the transmission cool down.
If the transmission is operated at higher temperatures on
a frequent basis, see "Scheduled Maintenance" in the
Index for the proper transmission maintenance intervals.