Case IH 520550-03 - BCM – BCM: Left extended arm turn indicator - short circuit to B+

The electrical circuit responsible for operating the left turn signal on the machine's extended arm is receiving unintended, continuous battery voltage (B+). This typically causes the BCM to disable the circuit to protect itself, or it may cause the turn signal to stay illuminated constantly without flashing.

• MAGNUM AFS Connect
• Magnum series
• Steiger series
• Puma series
• Maxxum series
• Axial-Flow series
• Backhoe loaders (580, 590, 695 series)

1. 1

   Isolate the circuit by turning the ignition off and disconnecting the wiring harness plug at the left extended arm turn indicator and the corresponding plug at the BCM.

2. 2

   Test for voltage by turning the ignition back on and measuring the voltage on the turn indicator signal wire. If it reads battery voltage while disconnected from the BCM, the wire is shorted to a power source in the harness.

3. 3

   Physically inspect the harness connectors and wires, specifically checking the pivot points where the extended arm folds out. Look for pinched wires, rubbed-through insulation, or corrosion bridging the pins inside the connectors.

4. 4

   If the wiring tests fine (no voltage on the wire when disconnected), check if the short to B+ is internal to the turn indicator assembly or the BCM itself.

1. 1

   Disconnect Power

   Disconnect the negative battery cable to prevent electrical arcing or further damage to the BCM during repair.

2. 2

   Expose the Harness

   Open the wire loom along the left extended arm, focusing on hinge points and areas where the harness routes near metal brackets.

3. 3

   Repair the Wiring

   If a chafed wire is found touching a power supply wire, cut out the damaged section. Splice in a new piece of appropriately gauged wire using weather-sealed, heat-shrink butt connectors.

4. 4

   Replace the Component (if necessary)

   If the wiring harness is intact and tests show the short is inside the light fixture, unbolt the left extended arm turn indicator assembly, disconnect the pigtail, and install a new OEM indicator.

5. 5

   Reassemble and Reconnect

   Re-loom the wiring harness, ensuring it is secured with zip ties away from pinch points. Reconnect the BCM and the turn indicator plugs.

6. 6

   Clear Codes and Test

   Reconnect the battery. Use a diagnostic tool (such as the Jaltest Agricultural kit or CNH EST) to clear the stored BCM fault code. Turn on the hazard lights or left turn signal to verify proper operation.