2009 Chevrolet Avalanche Owner's Manual - Page 413

Overheated Engine Protection Operating Mode If an overheated engine condition exists and the ENGINE POWER IS REDUCED message is displayed, an overheat protection mode which alternates firing groups of cylinders helps prevent engine damage. In this mode, you will notice a loss in power and engine performance. This operating mode allows the vehicle to be driven to a safe place in an emergency. Driving extended miles (km) and/or towing a trailer in the overheat protection mode should be avoided. Notice: After driving in the overheated engine protection operating mode, to avoid engine damage, allow the engine to cool before attempting any repair. The engine oil will be severely degraded. Repair the cause of coolant loss, change the oil and reset the oil life system. See Engine Oil on page 5-15. Engine Fan Noise The vehicle has electric cooling fans. You might hear the fans spinning at low speed during most everyday driving. The fans can turn off if no cooling is required. Under heavy vehicle loading, trailer towing, and/or high outside temperatures, or if you are operating the air conditioning system, the fans can change to high speed and you might hear an increase in fan noise. This is normal and indicates that the cooling system is functioning properly. The fans change to low speed when additional cooling is no longer required. 5-33