Cache is not at posted coords, but you will need to go there to get coords for the final. The posted coords take you to a light pole. On the light pole is a number. Enter the number on the light pole. You are typing in the 6 digit number, NOT the number starting with 'P'. Type the number into Certitudes. Here is the link to certitudes:
You can validate your puzzle solution with certitude.
When verifyed, it will give you final coordinates. At the new coordinates is the Final Stage. Cache is pill bottle in a stump, litterally.