2003 GMC Sierra 1500 Pickup Owner's Manual - Page 413

If No Steam Is Coming From Your Engine An overheat warning, along with a low coolant message, can indicate a serious problem. For more information, see Driver Information Center (DIC) OR page 3-50. If you get an engine overheat warning with no low coolant message, but see or hear no steam, the problem may not be too serious. Sometimes the engine can get a little too hot when you: If you no longer have the overheat warning, you can drive. Just to be safe, drive slower for about 10 minutes. If the warning doesn't come back on, you can drive normally. If the warning continues, pull over, stop, and park your vehicle right away. If there's still no sign of steam, push down the accelerator until the engine speed is about twice as fast as normal idle speed for at least three minutes while you're 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" listed previously in this section. Climb a long hill on a hot day. Stop after high speed driving. Idle for long periods in traffic. Tow a trailer. See "Driving on Grades" under Towing a Trailer on page 4-66. If you get the overheat warning with no sign of steam, try this for a minute or so: 1. If you have an air conditioner and it's on, turn it off. 2. Turn on your heater to full hot at the highest fan speed and open the window as necessary. You may decide not to lift the hood but to get service help right away. 3. If you're in a traffic jam, shift to NEUTRAL (N); otherwise, shift to the highest gear while driving - AUTOMATIC OVERDRIVE @ or DRIVE (D) for automatic transmissions. 5-38