GM has just updated their Customer Specific Requirements for IATF 16949:2016.
The new version GM CSR was published on the 1st of May 2019. The certification scope must include both IATF 16949 and the accompanying IATF 16949 GM Customer Specific Requirements.
All IATF 16949 requirements, including the requirements of this document, shall be addressed in the organization’s quality management system.
The document comes into force on the 1st of June 2019.
You can find the full text of the document here.