A common point of failure on the 508, this unit sits on top of the battery and manages power protection and distribution. How to Read Peugeot Wiring Diagrams
This explains why a faulty BSI can kill horn even if relay and horns are good. peugeot 508 wiring diagram
The Peugeot 508 utilizes a centralized "multiplex" architecture where multiple electronic control units (ECUs) communicate over a digital bus. A common point of failure on the 508,
: If one LIN device fails (e.g., driver’s window), others on same LIN (passenger window) may still work if wiring intact. But a short to ground on LIN kills all. peugeot 508 wiring diagram
: In the diagram, look for BBDA (Battery distribution box) or CA00 (connector to BSI).