A method and related apparatus are disclosed of guaranteeing VIN registration to a vehicle's ECU. A vehicle identifier is entered into a production control system connected to a network. The entered vehicle identifier is compared with an expected vehicle identifier. If a match is obtained between the entered and expected vehicle identifiers, the vehicle identifier is sent from the production control system to a vehicle Immobilizer. A vehicle identifier acknowledgement is received at the production control system from the vehicle Immobilizer. The production control system verifies the vehicle identifier embedded in the acknowledgement. If a match is obtained, an information record associated with the vehicle identifier is sent from the production control system to the vehicle Immobilizer. An information record acknowledgement is received at the production control system from the vehicle Immobilizer. The production control system verifies the information record embedded in the acknowledgement. If a match is obtained, an authorization message is sent from the production control system to the vehicle Immobilizer. The vehicle identifier and the associated information record from the vehicle Immobilizer are written into an electronic control unit incorporated into the vehicle in response to the authorization message. The vehicle Immobilizer then continues to write other data into the vehicle's ECU. After all the writing is complete, the vehicle Immobilizer reads from the vehicle's ECU the vehicle identifier and the information record, and sends them back to the production control system for final verification. If the two pieces of information from the ECU match the two pieces of information held by the production control system, the production control system sends a complete message to the Immobilizer and records the VIN registration record in the central database. Upon receiving the complete message, the Immobilizer resumes to its ready state and the ECU data registration process is complete.