2005 Monte Carlo key stopped working in both the door and ignition. Key is older and starting to look worn but showed no issues before it quit working. Lost the other key and FOB a while ago so this is my only key right now. Tried pulling the positive cable to the battery with no results. Where's the next place to look?

 

If the key is not working in the door or ignition and looks pretty worn, it may be worn to the point it's simply the key that is the problem. With the VIN, the dealer can cut a new key (not sure what else they require to validate you own the car). Since your current key is not working, do NOT have a shop cut a copy (you would be copying a bad key). The dealer method, they cut a fresh key from the actual specs for that VIN without the original key.