1. Insert the original, already programmed key in the ignition and start the engine.
2. After the engine has started, turn the key to off and remove the key.
3. Insert the key to be programmed and turn it to on within 10 seconds of removing the original key.
4. The security light will turn off once the key has been programmed. It may not be apparent if the security lightwent on due to how quickly the key is programmed. If your vehicle does not have a security light (04-07 GrandPrix, Bonneville, Impala) wait 10 minutes and 45 seconds to make sure the key has been programmed.
5. Repeat steps 1 through 5 if additional keys are to be programmed.
2012 GMC Yukon Key Programming