2002 GMC Envoy Owner's Manual - Page 234

The TRAC OFF light on the button will come on under the following conditions: D The Traction Assist System is turned off, either by pressing the TAS on/off button or turning off the automatic engagement feature of the TAS. operate in this gear. This is normal. D The transmission is in FIRST (1); TAS will not D The vehicle is driven on an extremely rough road. When the vehicle leaves the rough surface, slows down or stops, the light will go off and TAS will be on again. This is normal. To turn the system on or off press the TAS on/off button located near the shift lever. If you used the button to turn the system off, the TRAC OFF light on the button will come on and stay on. D A Traction Assist System, Anti-Lock Brake System or engine-related problem has been detected and the vehicle needs service. The Traction Assist System, as delivered from the factory, will automatically come on whenever you start your vehicle. To limit wheel spin, especially in slippery road conditions, you should always leave the system on. But you can turn the TAS off if you ever need to. You should turn the TAS off if your vehicle ever gets stuck in sand, mud or snow and rocking the vehicle is required. See "Rocking Your Vehicle" in the Index. You can turn the system back on at any time by pressing the button again. The TRAC OFF light on the button should go off. If desired, you can change the TAS automatic engagement feature so that the system will not come on automatically when the engine is started. To do so: 1. Park the vehicle with the ignition off and the transmission in PARK (P). 2. Turn the ignition to RUN; do not start the engine. 4-10