1997 GMC Sonoma Owner's Manual - Page 64

Engine Coolant Heater (Option) IA 3. Plug it into a normal, grounded 110-volt AC outlet. CAUTE-N: I Plugging the cord into an ungrounded outlet could causean electrical shock.Also, the wrong kind of extension cord could overheat and cause a fire. You could be seriously injured. Plug the cord intoa properly grounded three-prong 110-volt AC outlet. If the cordwon't reach, use a heavy-duty three-prong extension cord rated for at least 15 amps. "VORTEC" 4300 Engine 2.2L Engine 4. Before starting the engine, be sure to unplug and store to the cord as it was before keep it away from moving engine parts. If you don't, it could be damaged. In very cold weather, 0°F (- 18"C) or colder, the engine coolant heater can help. You'll get easier starting and better fuel economy during engine warm-up. Usually, the coolant heater should be plugged in a minimum of four hours prior to starting your vehicle. To Use the Coolant Heater 1. Turn off the engine. How long should you keep the coolant heater plugged in? The answer depends on the outside temperature, the kind of oil you have, and some other things. Instead of trying to list everything here, we ask that you contact your GM dealer in the area where you'll be parking your vehicle. The dealer can give you the best advice for that particular area. 2. Open the hood and unwrap the electrical cord. 2-16