A few months back I locked the trunk lever using the key I am using to start the car with. A few months later the same key is unable to unlock the lever. It inserts ok but will not turn, I'm afraid if I use any more force I will break either the key or the lock.

The only other key I have is the valet key (grey color) which is designed to only start and unlock the doors.

Is it possible the key is so worn down the tumblers aren't catching in the lock? What are my options for a replacement key? Cost?

 

First I'd try working & lubricating that lock cylinder. It probably doesn't get much action, so maybe the tumblers are corroded??

 

you should also have a key w/o a chip that is used for the doors/trunk/glove box... but regardless.. the main key can do all of the above.

I would suggest turning as hard as you can, if it never get used then you will need to lube it and keep trying. I know when i was trying to put my back seats down, you need to insert the key and twist to unlock the back seats. i almost broke the key unlocking it but it worked with some brute strength

 

Not quite, phantom. The valet key (grey plastic) DOES have an immobilizer chip because that's needed to start the engine.

I also wouldn't try to force the key to turn - might risk breaking the key. Work the tumblers (with some oil) by putting the key in & out repeatedly.