once you get all the way in to it, there is a tiny button on the outside of the cylinder that needs to be pushed inward and out of its hole in the housing. That little button wont push unless the key is in and turned to run position.
If you have a locking wheel mechanism in that model there is a steel plate almost completely covering this button you're looking for. You wont have to remove that steel plate if you have a small angled tool like a dental pick to use.