2010 GMC Sierra 1500 Crew Cab Owner's Manual - Page 265

Engine Coolant Temperature Gauge Tire Pressure Light For vehicles with a tire pressure monitoring system, this light comes on briefly when the engine is started. It provides information about tire pressures and the Tire Pressure Monitoring System. When the Light is On Steady United States Canada This indicates that one or more of the tires is significantly underinflated. A tire pressure message in the Driver Information Center (DIC), can accompany the light. See Driver Information Center (DIC) on page 4‑50 for more information. Stop and check the tires as soon as it is safe to do so. If underinflated, inflate to the proper pressure. See Inflation - Tire Pressure on page 6‑80 for more information. This gauge shows the engine coolant temperature. It also provides an indicator of how hard the vehicle is working. During a majority of the operation, the gauge will read 210°F (100°C) or less. If the vehicle is pulling a load or going up hills, it is normal for the temperature to fluctuate and go over the 235°F (113°C) mark. However, if the gauge reaches the 260°F (125°C) mark, it indicates that the cooling system is working beyond its capacity. See Engine Overheating on page 6‑39. 4-41