GMC Troubleshooting Questions? Ask a Mechanic for Answers
Have you tried a 30 minute security relearn?
yes let me know when you are available today
a fully charged battery and a 30 min cycle
The learn procedure is as follows:
Turn the lock cylinder all the way to the crank mode so the magnet on the lock cylinder can travel pass the Pass Lock sensor. Now let go of the key so it can return to the run position. The 5 Volt line will now be pulled to a value below 5 volts and the security light may begin to start flashing or just remain on solid. Some vehicles may start up and stall or may not crank at all. You must leave the ignition key on for 10 minutes and place a battery charger on the battery if needed in case the battery is low on charge. After 10 minutes you will see the security light go out or just stop flashing and then go out. At this point you turn the key off for 5 seconds. After 5 seconds you turn the lock cylinder to the crank position again to repeat the same process .You must perform this process 3 times for a total of 30 minutes of wait time. On your 4th attempt the vehicle should start up and continue to run.
sometimes you need to do it a few times..if not likley the key switch aassembly failed