B2545

Step 1: Remove the system power relay from its socket and visually inspect both the relay pins and socket terminals for signs of corrosion, melting, water intrusion, or crossed/bent terminals. Check for any foreign debris causing shorts between terminals.

Step 2: With the relay removed and ignition OFF, use a digital multimeter to measure voltage on the relay control pin at the relay socket (consult wiring diagram for specific pin). Reading should be 0 volts; if battery voltage is present, the short is in the wiring harness or BCM.

Step 3: Inspect the complete wiring harness from the relay socket to the BCM connector for damage, particularly in areas where the harness passes through firewalls, near sharp metal edges, or routing near hot components. Look for melted, chafed, or pinched insulation.

Step 4: Disconnect the BCM connector and re-measure voltage at the relay socket control pin with ignition OFF. If voltage disappears, the BCM has an internal short and requires replacement. If voltage remains, trace and repair the harness short between relay and BCM.

Step 5: If no external wiring faults are found, test the suspect relay by measuring resistance between the coil terminals and the power/load terminals using an ohmmeter. Resistance should be infinite (open circuit) between coil and power sides; continuity indicates internal relay failure.

Step 6: After repairs, reinstall all components, clear codes, and monitor the system through multiple key cycles and vehicle operations to confirm the short circuit is eliminated and the BCM can properly control the relay.