Case IH 520581-05 - BCM – BCM (Body Control Module): Marker light front & rear left - open circuit

The system has detected an "open circuit" (FMI 5 translates to "Current Below Normal or Open Circuit") on the electrical circuit responsible for powering the left-side front and rear marker/clearance lights. The module is sending voltage to the circuit but is not seeing the expected current draw return, which is typically caused by a blown bulb, a severed wire, a disconnected plug, or a failed internal driver inside the control module.

• MAGNUM AFS Connect
• STX275
• STX325
• STX375
• STX425
• STX450
• STX500
• Steiger 280
• Steiger 330
• Steiger 335
• Steiger 380
• Steiger 385
• AFS Connect Magnum
• 5088
• 6088
• 7088
• 7120
• 7240
• 8240
• 9240

1. 1

   Perform a visual bulb check on the left front and left rear marker lights for burnt-out incandescent bulbs.

2. 2

   Check for recent LED retrofits; aftermarket LEDs draw less current and can trick the BCM into throwing a false open circuit code.

3. 3

   Inspect the wiring harness leading to the left marker lights for pinch points, corrosion inside connectors, or moisture intrusion.

4. 4

   Perform a multimeter continuity test by disconnecting the marker light housings and testing the wiring harness back to the BCM bulkhead connector.

1. 1

   Power Down

   Turn off the machine and disconnect the negative battery terminal to prevent electrical spikes while servicing the BCM circuits.

2. 2

   Access the Lights

   Remove the lenses or housings for the left front and left rear marker lights.

3. 3

   Replace or Test Bulbs

   Remove the bulbs. If the filament is broken, replace the bulb. If using LEDs, ensure they are "CAN-bus error-free" (meaning they have built-in load resistors to mimic incandescent current draw).

4. 4

   Clean Contacts

   If the bulbs are intact, spray the light sockets and harness connectors with electrical contact cleaner. Apply a small amount of dielectric grease to prevent future moisture corrosion.

5. 5

   Repair Wiring

   If the multimeter test showed a broken wire, trace the harness along the frame/cab to locate the break. Splice the wire using a proper solder joint and weather-resistant heat-shrink tubing. Do not use quick-splice connectors on BCM-monitored circuits.

6. 6

   BCM Reset/Test

   Reconnect the battery. Turn the headlight/marker switch on. If the lights illuminate, use a diagnostic scan tool to clear the 520581-05 fault code.

7. 7

   Module Replacement

   If the wiring is 100% intact, the bulbs are good, and the lights still do not work (and the code immediately returns), the BCM has likely suffered a failed internal MOSFET driver. The BCM will need to be sent out for repair or replaced and reprogrammed by a dealer.