031799 is a fault stored in your BMW's memory (an ISTA fault code, not a standard OBD-II P-code).
What it means: Head unit (HU-H) — app-connection function temporarily restricted. The infotainment briefly lost or limited its link to connected smartphone apps (e.g. the My BMW app or Apple CarPlay/Android Auto). This is NOT a faulty part: it's a connectivity/back-end condition — a dropped phone or data connection, or a temporary service restriction. Nothing to replace — it clears itself once the phone connection or online service is back. Informational, nothing to worry about.
