Think City Programming Failure Due to Missing Original Key

This cause is confirmed if the immobilizer system requires an active, previously programmed key to authorize the introduction of a new transponder. Many legacy Ford-based systems are configured to prevent the addition of new keys unless a valid master key is present in the ignition during the programming sequence. Verify this by attempting to access the 'Add Key' function in the diagnostic software; if the system prompts for a master key, this requirement is active.

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