Case IH 520584-03 - BCM – BCM: Left brake indicator light - short circuit to B+ (Battery Positive)

The control module has detected that the circuit supplying power to the left brake indicator light is receiving battery voltage (B+) when it should not be, or there is a direct short to a power source in the wiring harness or the light assembly itself.

• MAGNUM AFS Connect
• Magnum 250 AFS Connect
• Magnum 280 AFS Connect
• Magnum 310 AFS Connect
• Magnum 340 AFS Connect
• Magnum 380 AFS Connect
• Magnum 400 AFS Connect

1. 1

   Inspect the rear left tail light/brake light assembly for physical damage, water ingress, or melted plastic.

2. 2

   Trace the wiring harness from the left brake light back to the BCM for pinched wires, chafing, or melted insulation.

3. 3

   Disconnect the left brake light and BCM harness connectors and check for corrosion, moisture, or bent pins.

4. 4

   With the brake pedal released and light disconnected, measure voltage at the brake light connector (12V indicates a short to power).

5. 5

   Check for continuity between the brake light signal wire and known B+ wires in the same harness bundle.

1. 1

   Disconnect Power

   Turn off the tractor and disconnect the negative battery terminal to prevent accidental arcing during the repair.

2. 2

   Isolate the Short

   Disconnect the BCM connector that houses the left brake light pin, as well as the connector at the left brake light itself.

3. 3

   Repair the Wiring

   If the multimeter test confirmed a short in the harness, unloom the affected section of the wiring harness. Locate the fused/chafed wires. Cut out the damaged section, solder in a new piece of appropriately gauged wire, and seal it with dual-wall adhesive heat shrink. Re-loom the harness.

4. 4

   Replace the Light Assembly

   If the wiring harness tests perfectly fine (no short to B+ when disconnected from the light), the short is likely internal to the LED/bulb assembly. Remove the retaining screws on the left rear fender light housing and install a new brake light assembly.

5. 5

   Reassemble and Clear Codes

   Reconnect all BCM and light connectors. Reconnect the battery. Turn the ignition on and use the AFS Pro 1200 monitor (or an electronic service tool) to clear the inactive 520584-03 fault code.

6. 6

   Verify Operation

   Depress the brake pedal to ensure the left brake light illuminates correctly and verify that the fault code does not return.