If your model has a Subsystem block that does not achieve full coverage, you can convert it to model referenced in a Model block. Convert Subsystems to Referenced Models describes how to convert a subsystem to a referenced model. You can then follow the steps described in Achieve Missing Coverage in Referenced Model.
You cannot convert some subsystems to Model blocks. To test a subsystem to see
if you can convert it to a Model block, use the
Simulink.SubSystem.convertToModelReference function. If that function
cannot convert the subsystem, an error message describes why the conversion
It is possible that you have a Stateflow® chart or a MATLAB Function block that does not achieve full coverage. You cannot convert Stateflow charts and MATLAB Function blocks to referenced models.
When you cannot use a Model block, follow the steps described in Achieve Missing Coverage in Closed-Loop Simulation Model.