Key deactivation is intended to secure keys that have been stored in the vehicle. A deactivated key will not start the vehicle. Keys become deactivated when left inside the vehicle when the alarm is armed. For example, if the vehicle is locked by another key, or if keyless locking arms the alarm. Keys become deactivated if left inside the vehicle when closing the tailgate, bootlid or taildoor while the alarm is armed.
To reactivate a key: