2003 GMC Sierra 1500 Pickup Owner's Manual - Page 221

TRANSMISSION HOT If the transmission fluid temperature becomes high, the message center will display this message. 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 turnoff 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. The following situations can cause the transmission to operate at higher temperatures: 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. A temporary solutionto 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 on page 6-5 for the proper transmission maintenance intervals. TRANS HOT IDLE ENGINE (Allison Transmission Only) If the transmission fluid in the vehicle gets hot, this message will appear on the DIC, and you will hear a chime. The chime will stop when the transmission fluid temperature is less that 265°F (129°C). Driving with the transmission fluid temperature high can cause damage to the vehicle. Stop the vehicle and let it idle to allow the transmission to cool. This message will clear when the fluid temperature reaches a safe level. Notice: If you keep driving your vehicle with the transmission TRANS HOT...IDLE ENGINE message displayed, you can damage the transmission. This could lead to costly repairs that may not be covered under your warranty. 3-66