This means the key seed in the ECM has been changed from the factory key seed. Think of the key seed as the password to allow the ECM to be accessed and reprogrammed. If this has been changed from the factory original, then we will not be able to program the ECU. Likewise, the Dealer will not be able to either. This is sometimes changed by another tuning company. Many times to protect a custom operating system. In order to use ours, or another tuning device, you will need a different ECM.