Case IH 520594-06 - BCM – BCM: License plate lights - short circuit to ground

The control module has detected that the voltage intended for the license plate illumination circuit is finding a direct path to the ground (the machine's chassis or a ground wire) before passing through the bulb. This typically results in a blown fuse or the module shutting down the circuit to protect the wiring harness from melting or catching fire.

• MAGNUM AFS Connect
• Magnum 400 AFS Connect
• Magnum 310
• Magnum 250
• AFX8010
• Farmall 120U
• Puma 165-225 CVX

1. 1

   Visually inspect the wiring harness leading to the license plate lamp for pinched wires, chafing against the metal frame, or degraded insulation.

2. 2

   Check connectors and splices, including the jumper harness plugged into connector X302 (on combines) or the 2-pin/3-pin electrical connectors at the rear fender harness (on tractors).

3. 3

   Inspect the license plate lamp assembly for water ingress, heavy corrosion inside the bulb socket, or a melted base bridging power and ground contacts.

4. 4

   Isolate the short by disconnecting the license plate light connector and using a multimeter to check for continuity to ground on the power supply pin of the harness. If the short remains, the issue is in the wiring harness; if it disappears, the issue is internal to the lamp assembly.

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the battery ground cable to ensure the circuit is completely unpowered.

2. 2

   Access the Assembly

   Locate the license plate lamp assembly (usually mounted on the rear license plate support bracket, part of the rear tail light combination, or on the cab roof).

3. 3

   Disconnect and Remove

   Unplug the electrical connector from the lamp. Remove the mounting nuts/bolts (typically M5 or M6 hardware) securing the lamp support bracket.

4. 4

   Repair Wiring (If Applicable)

   If the diagnostic check revealed a chafed wire on the harness, cut out the damaged section, solder in a new wire, and seal it with marine-grade heat-shrink tubing. Alternatively, replace the dedicated license plate light wire harness.

5. 5

   Replace the Lamp (If Applicable)

   If the socket is corroded or internally shorted, discard the old housing. Install the new base, insert a new 12V bulb, and snap on the new lens.

6. 6

   Reassemble

   Bolt the lamp assembly back onto the support bracket. Reconnect the electrical harness.

7. 7

   Test and Clear Codes

   Reconnect the battery. Turn on the marker/headlights to verify the license plate light illuminates. Access the AFS Connect monitor or diagnostic menu to clear the inactive 520594-06 BCM fault code.