Case IH 520603-03 - BCM – BCM: Short circuit to B+ on Work lamp #10

The control module is detecting voltage on the work lamp's ground or control circuit that shouldn't be there, usually caused by a wiring harness rubbing against a live power wire, or an internal short inside the LED work lamp assembly itself.

• MAGNUM AFS Connect
• Magnum AFS Connect Series (Magnum 180, 200, 220, 240, 250, 280, 310, 340, 380, and 400)
• Optum AFS Connect
• Steiger / Quadtrac AFS Connect

1. 1

   Locate the BCM Fuses: Access the cab fuse and relay panel behind the operator's seat by removing the rubber liner from the tray in the rear cab wall and turning the large screws 1/4 turn.

2. 2

   Check BCM Power Supplies: Verify the integrity of the BCM supply fuses (F-003, F-004, F-005, and F-006, all 50 Amp) and the Front Work Lights fuse (F-001, 25A).

3. 3

   Isolate the Lamp (Internal Short Check): Disconnect the electrical connector directly at Work Lamp #10. Turn the machine on and activate the work lights. If the code changes from a 'short to B+' (03) to an 'open circuit' (05), the short is internal to the lamp assembly.

4. 4

   Inspect the Wiring Harness (Wiring Short Check): If the code remains a 'short to B+' with the lamp unplugged, trace the wiring harness from Work Lamp #10 back to the BCM. Look for pinched wires, melted insulation, or chafing where the wire might be touching a 12V power source.

1. 1

   Disconnect Power

   Turn off the tractor and disconnect the battery to prevent electrical spikes during repair.

2. 2

   Access the Component

   Depending on the diagnostic results, access either the damaged section of the wiring harness or the faulty work lamp.

3. 3

   Repair the Harness

   If a short to B+ was found in the wiring, cut out the melted or chafed section of the wire. Splice in a new section of wire using weather-sealed heat-shrink butt connectors. Secure the harness away from pinch points.

4. 4

   Replace the Lamp

   If the lamp was internally shorted, unbolt the work lamp from its bracket on the cab roof or pillar. Mount the new LED work lamp and plug it into the factory harness.

5. 5

   Reassemble and Clear Codes

   Reconnect the battery. Turn the ignition on and use the AFS Pro 1200 monitor or a diagnostic scan tool to clear the inactive 520603-03 fault code. Test the work lights to ensure proper operation.