DTC U0431: Invalid Data Received From Body Control Module "A"
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.
DTC detecting condition:
When the ignition switch is ON, error data from the front relay control module is received for 4 seconds or more.
NOTE:
Perform the diagnosis for LAN system. Ref. to LAN SYSTEM (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE