1998 GMC Envoy Owner's Manual - Page 70

Resynchronization Resynchronization may be necessary due to the security method used by this system. The transmitter does not send the same signal twice to the receiver. The receiver will not respond to a signal it has been sent previously. This prevents anyone from recording and playing back the signal from the transmitter. To resynchronize your transmitter, stand close to your vehicle and press and hold the LOCK and UNLOCK buttons on the transmitter at the same time for seven seconds. The door locks should cycle to confirm synchronization. If the locks do not cycle. see your dealer for service. LiftgateLiftglass It can be dangerous to drive with the liftgate or liftglass open because carbon monoxide (CO) gas can come into yourvehicle. You can't see or smell CO. It can cause unconsciousness and even death. If'you must drive with the liftgate liftglass or open or if electrical wiringor other cable connections must pass through the seal between the body and the liftgate liftglass: or Make sure all windows are shut. Turn the fan on your heating or cooling system to its highest speed with the setting on any airflow selection except RECIRCULATION. Thatwill force outside air into your vehicle. See "Comfort Controls" in the Index. If you have air outlets onor under the instrument panel, open them the way. all See "Engine Exhaust" in the Index. 2-9