Repair Instructions
WARNING: This page is about a different car, the 2020 Buick Regal and 2019 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.
Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification
After any repair, perform DTC P0420 Circuit/System Verification, to verify the performance of the component: Catalytic Converter - Refer to: DTC P0420 or P0430