2005 GMC Sierra 1500 Pickup Owner's Manual - Page 433

If you get the overheat warning with no sign of steam, try this for a minute or so: 1. If your air conditioner is on, turn it off. 2. Turn on your heater to full hot at the highest fan speed and open the windows as necessary. 3. If you are in a traffic jam, shift to NEUTRAL (N); otherwise, shift to the highest gear while driving - DRIVE (D) or THIRD (3). If you no longer have the overheat warning, you can drive. Just to be safe, drive slower for about 10 minutes. If the warning does not come back on, you can drive normally. If the warning continues, pull over, stop, and park your vehicle right away. If there is still no sign of steam and your vehicle is equipped with an engine-driven cooling fan, push down the accelerator until the engine speed is about twice as fast as normal idle speed for at least three minutes while you are parked. If there is still no sign of steam and your vehicle is equipped with an electric engine cooling fan, idle the engine for three minutes while you are parked. If you still have the warning, turn off the engine and get everyone out of the vehicle until it cools down. Also, see "Overheated Engine Protection Operating Mode" later in this section. You may decide not to lift the hood but to get service help right away. Overheated Engine Protection Operating Mode (V8 Engines Only) If an overheated engine condition exists and the REDUCED ENGINE POWER 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 your 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 (Gasoline Engine) on page 5-20. 5-39