2008 GMC Envoy Owner's Manual - Page 282

4. Follow the dolly manufacturer's instructions to attach and secure the vehicle being towed to the dolly and then the loaded dolly to the tow vehicle. Use an adequate clamping device to ensure that the front wheels are locked into the straight position. 5. Release the parking brake only after the vehicle being towed is firmly attached to the towing vehicle. 6. Turn the ignition to LOCK. If the tow vehicle will not be started or driven for six weeks or more, remove the battery cable from the negative terminal (post) of the battery. The system also has an internal clock to prevent overheating if the inflator is used for prolonged periods. If the system overheats, all leveling function stops until the system cools down. During this time, the indicator light on the air inflator switch will be flashing. The ignition has to be on for the system to inflate, in order to raise the vehicle to the standard ride height after loading. The system can lower the vehicle to the standard ride height after unloading with the ignition on and also for up to 30 minutes after the ignition has been turned off. You may hear the compressor operating when you load your vehicle, and periodically as the system adjusts the vehicle to the standard ride height. Load leveling will not function normally with the inflator hose attached to the inflator outlet. Remove the inflator hose from the outlet during loading and unloading. If the vehicle is parked for an extended period of time, some bleed down of the suspension is normal. Upon starting the vehicle, proper height will be achieved. Electronically Controlled Air Suspension System Your vehicle may be equipped with an electronically controlled air suspension system that automatically keeps your vehicle level as you load and unload. The system includes a compressor, two height sensors and two air springs supporting the rear axle. 4-44