GMC Troubleshooting Questions? Ask a Mechanic for Answers
Hello and welcome!
Some electrical fault tracing will be needed to properly diagnose the problem. I can help you with the most common causes if you want to try replacing some parts, or help fault tracing the electrical circuits.
First you will need to remove the steering column cover, under this cover there is a electronic solenoid that needs to activate to allow the key to turn to the off position. this is used to prevent the key from being turned off when the gear shifter is in gear and not in park. You can push on the bottom of this solenoid and the key should be able to release. The solenoid is located next to the ignition switch.
The most common cause for failure is a micro switch in the gear shift assembly to fail. This switch is integral to the shift unit and will need to be replaced.