How do you reset anti theft on 1998 gmc Yukon?

To reset the anti-theft system on a 1998 GMC Yukon, first ensure that the vehicle is in the "Off" position. Insert the key into the ignition and turn it to the "On" position without starting the engine, then leave it in this position for approximately 10 minutes until the security light turns off. After that, turn the key back to the "Off" position, wait a few seconds, and then attempt to start the engine. If the system still does not reset, you may need to consult the owner's manual or a professional mechanic for further assistance.