2003 GMC Envoy Owner's Manual - Page 337

Vehicle Storage If you're not going to drive your vehicle for 25 days or more, remove the black, negative (-) cable from the battery. This will help keep your battery from running down. Jump Starting If your battery has run down, you may want to use another vehicle and some jumper cables to start your vehicle. But please use the following steps to do it safely. Batteries have acid tnat can burn you and gas that can explode. You can be badly hurt if you aren't careful. See "Jump Starting" next for tips on working around a battery without getting hurt. Contact your dealer to learn how to prepare your vehicle for longer storage periods. Also, for your audio system, see Theft-Deterrent Feature (RDS Radios) on page 3-105. Batteries can hurt you. They can be dangerous because: They contain acid that can burn you. They contain gas that can explode or ignite. They contain enough electricity to burn you. If you don't follow these steps exactly, some or all of these things can hurt you. 5-42