Case IH 520601-03 - BCM – BCM: Work lamp #4 - short circuit to B+ (Luz de trabalho nº 4 - curto com B+)

The control module has detected a "short to B+" (Battery Positive) on the circuit responsible for powering Work Lamp #4. This means the circuit's voltage is reading high (12V-24V) when it shouldn't be, indicating that the control wire is either shorted directly to a constant power source in the wiring harness, or there is an internal short within the lamp assembly or the module itself.

• MAGNUM AFS Connect
• Case IH Magnum AFS Connect Series (e.g., Magnum 280, 310, 340, 380, 400)
• Case IH Steiger / Quadtrac AFS Connect Series

1. 1

   Pre-Scan and Clear: Verify if the code is active or stored. Clear the code via the AFS Pro 1200 monitor or diagnostic tool and cycle the work lights to see if it immediately returns.

2. 2

   Visual Inspection of the Lamp: Locate Work Lamp #4 (refer to the operator's manual for the exact cab/fender position of lamp #4, as configurations vary by lighting package). Check the lamp housing for physical damage, melted plastic, or water ingress.

3. 3

   Harness & Connector Check: Disconnect the lamp. Inspect the pigtail and the main harness connector for pushed-out pins, corrosion, or water bridging the terminals.

4. 4

   Voltage/Continuity Test: With the lamp disconnected and the work light switch off, use a multimeter to probe the power supply wire at the lamp connector. If it reads battery voltage (12V+), the wiring harness is shorted to a power wire somewhere between the BCM and the lamp. Jiggle the wiring harness along the cab roof/fender routing to see if the voltage fluctuates, which helps pinpoint chafed wires.

5. 5

   BCM Pin Check: If the harness tests fine, disconnect the corresponding connector at the BCM and check for internal bridging, corrosion, or bent pins.

1. 1

   Disconnect Power

   Turn off the ignition and disconnect the battery via the battery isolator switch to prevent further electrical damage.

2. 2

   Isolate the Short

   Based on the diagnostic tests, if the short is in the wiring harness, trace the harness from the lamp back to the cab entry point. Look for pinch points near cab mounts, fender brackets, or roof hinges.

3. 3

   Repair the Wiring

   If a chafed wire is found shorting against a constant 12V wire, cut out the damaged section. Splice in a new section of wire using weather-resistant heat-shrink butt connectors. Wrap the repaired section in protective loom or Tesa tape.

4. 4

   Replace the Lamp (If internally shorted)

   If the harness tests perfectly but the code only triggers when the lamp is plugged in, the LED driver board inside the work lamp has failed and shorted internally. Unbolt the lamp from its swivel bracket and install a replacement.

5. 5

   Reassemble and Test

   Reconnect the battery. Turn on the ignition and activate the work light circuit. Verify that Work Lamp #4 illuminates properly and that the 520601-03 fault code changes from "Active" to "Inactive" (or clears entirely).