2008 GMC Envoy Owner's Manual - Page 181

Highbeam On Light This light comes on when the high-beam headlamps are in use. The service four-wheel drive light comes on to indicate that there may be a problem with the drive system and service is required. Malfunctions can be indicated by the system before any problem is apparent, which may prevent serious damage to the vehicle. This system is also designed to assist your dealer in correctly diagnosing a malfunction. Check Gages Warning Light See Headlamp High/Low-Beam Changer on page 3-8 for more information. The check gages light will come on briefly when you are starting the engine. Service Four-Wheel Drive Warning Light This light should come on briefly when you turn on the ignition, as a check to show you it is working. If the light comes on and stays on while you are driving, check your coolant temperature and engine oil pressure gages to see if they are in the warning zones. 3-47