Circuit/System Description
WARNING: This page is about a different car, the 2013 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
The navigation radio communicates with the radio control assembly via serial data. If the radio receives an improper status response message, DTC B1020 will set.
This DTC indicates an internal ECU fault or a stuck button on the faceplate. No external circuits are involved.