DTC B1731: Central Gateway Control Module Can Register Stuck
WARNING: This page is about a different car, the 2022 Subaru WRX. However, it is still accessible from the selected car via links, so may be relevant.
Outline of diagnosis:
When the microcomputer was reset (power turned ON), a fail-safe judgment error was detected in one of the bus.
Trouble symptom:
CAN communication between the bus for which malfunction (register freeze) was detected and other bus is cut off.
NOTE:
If this DTC was detected, replace the central gateway control module. Ref. to BODY CONTROL/COMMUNICATION SYSTEM>CENTRAL GATEWAY CONTROL MODULE