1997 GMC Suburban Owner's Manual - Page 90

4. Before starting the engine, be sure to unplug and store the cord as it was before to keep it away from moving engine parts. If you don't, it could be damaged. How long should you keep the coolant heater plugged in? Theanswer 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. Automatic Transmission Operation There are several different positions for your shift lever.