how to activate the new key pf Cat 312D
I buy new key for Cat 312D but when turn the key the engine cannot start and Indicate in panel The Un Authorized key
if you have not master key you will should to use CAT ET and factory password. So you need to call of local dealer.
Sounds like you have a chip key. Last I saw of those they had a yellow cover instead of the black one. I believe there is a procedure to link it to the machine but don't know what it is. All those that came into our territory were somehow disabled so that any Cat key would work.