1) Disconnect the body integrated unit connector (B279).
2) Measure the voltage between body integrated unit connector and chassis ground using tester.
Connector & terminal
(B280) No. 7 (+) — Chassis ground (−):
Is the voltage 8.5 — 16.5 V?
Replace the body integrated unit.
Repair or replace the open or shorted circuit between body integrated unit and fuse.