2004 Pontiac GTO Owner's Manual - Page 220

If you get the overheat warning with no sign of steam, try this for a minute or so: 1. In heavy traffic, let the engine idle in NEUTRAL (N) while stopped. If it is safe to do so, pull off the road, with the parking brake applied, shift to PARK (P) or NEUTRAL (N) and let the engine idle while you get out and check that the cooling fan is working. 2. If the fan is working and the temperature gauge needle has not returned to its normal position within a few minutes, stop the engine and remove the ignition key. Look for leaks at the radiator hoses and connections, heater hoses and connections, radiator, and water pump. Be careful when checking these areas as they will probably still be hot. If you find a major leak or other problems that may have caused the engine to overheat, do not run the engine until these problems have been corrected. If you do not find anything wrong, you should check the engine coolant level. See Engine Coolant on page 5-25. You should also check the air intake area below the front bumper to ensure that it is clear of leaves and road grime. 3. Turn off your air conditioning and turn on your heater to full hot at the highest fan speed and open the window as necessary. 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, you can idle the engine for 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. You may decide not to lift the hood but to get service help right away. 5-30