2001 GMC Sierra 1500 Pickup Owner's Manual - Page 174

At approximately 265_F (130_C), the message center will display a TRANS FLUID HOT message and the transmission will enter a transmission protection mode. When the transmission enters the protection mode, you may notice a change in the transmission shifting patterns. The transmission will return to normal shifting patterns when the transmission fluid temperature falls below 260_F (127_C). See "Message Center" in the Index for further information. If the transmission fluid reaches temperatures of approximately 275_F (135_C) or greater, the message center will display a TRANS HOT...IDLE ENG warning message. Pull the vehicle off the roadway when it is safe to do so. Set the parking brake, place the transmission in PARK (P) and allow the engine to idle until the transmission temperature falls below 260_F (127_C). If the transmission continues to operate above 265_F (130_C), please contact your nearest dealer or the GM Roadside Assistance Center. NOTICE: If you keep driving your vehicle with the transmission temperature gage above the normal operating range, you can damage the transmission. This could lead to costly repairs that may not be covered under your warranty. The following situations can cause the transmission to operate at higher temperatures: D D D D D D Towing a trailer Hot outside air temperatures Hauling a large or heavy load Low transmission fluid level High transmission fluid level 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. 2-91