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In order to create a vehicle in the standard system, you first have to create a vehicle model.
You can use BAdI: Control Vehicle Master APIs (BAdI /DBE/BADI_VEHICLE_API) to copy default data from the vehicle model master to the vehicle master when you create a new vehicle. If you do not wish to use the default implementation of the BAdI, you can create a customer implementation.
You can also create a vehicle without a vehicle model. If you want to do this, there must be a material in the material master for this purpose. When you create the vehicle, you have to enter the material instead of the model, or you can implement your own logic for material determination in BAdI: Control Vehicle Master APIs.
If you create an order from the vehicle master, the vehicle data is copied to this order. To do this, implement BAdI: Control Vehicle Order (/DBE/VEHICLE_SALES).