A very common problem occurs when one of your keys breaks. The key may break outside of the lock or while in the lock. If it breaks outside of the lock, you need to take the broken pieces to a professional locksmith and have a new key originated. If the key is extremely worn, the locksmith must come to where the lock or vehicle is to ensure correct origination of a new key. Saturn vehicles along with older G.M. vehicles with single sided keys are notorious for worn keys that are not easy to decode.
If the key has broken off in the lock, do yourself a favor and call a Professional Locksmith to extract the broken piece from the lock. Locks contain many small springs and parts that can easily be damaged from someone not skilled at lock service, attempting to remove a broken key. Weekly, we see the results of someone attempting to remove a key and inadvertently destroying the lock or making the key extraction even more difficult. Replacing the lock will definitely cost far more than having the key extracted by a professional.
To avoid the problem of a broken key, replace any keys that have small fractures or crack in them as well as worn keys. Also, have a professional look at the lock and key when they become hard to operate. Most often, a lock that does not operate easily may be the result of a worn key. I have seen numerous vehicle locks replaced by mechanics when only the key was worn, costing the motorists far more than would have been necessary to replace the key.