Case IH 520568-05 - BCM – BCM: Door light auto driver - open circuit

The Body Control Module (BCM) is attempting to send power to the automatic cab door/courtesy light, but it is not detecting the expected electrical load. An 'open circuit' typically indicates a broken wire, an unplugged connector, or—most commonly—a blown light bulb.

• MAGNUM AFS Connect
• Magnum 180
• Magnum 200
• Magnum 220
• Magnum 240
• Magnum 250
• Magnum 280
• Magnum 310
• Magnum 340
• Magnum 380
• Magnum 400 AFS Connect

1. 1

   Inspect the interior door light bulb/LED for burnout (most frequent cause of an open circuit code on a lighting driver)

2. 2

   Check the electrical connector at the cab interior light assembly for loose, backed-out, or corroded pins

3. 3

   Perform a continuity test on the wiring harness between the BCM output pin for the door light and the light assembly itself, paying special attention to areas where the harness flexes

4. 4

   Ensure the ground circuit for the door light is secure and free of corrosion

1. 1

2. 2

   Isolate power

   Turn off the tractor and disconnect the battery or turn off the battery isolator switch.

3. 3

   Access the light

   Remove the lens cover from the cab interior door light.

4. 4

   Test the bulb

   Remove the bulb/LED and test it with a multimeter. If it lacks continuity (blown), replace the bulb, restore power, and test the door light operation. This will likely clear the code.

5. 5

   Test for voltage

   If the bulb is good, reinstall it. Restore battery power, open the cab door, and use a multimeter to check for voltage at the light connector.

6. 6

   Trace the harness

   If no voltage is present at the connector, trace the wiring harness back to the BCM. Look for pinch points, chafing, or broken wires.

7. 7

   Repair wiring

   Repair any broken wires using appropriate automotive wire and weather-sealed heat-shrink connectors.

8. 8

   Evaluate BCM

   If the wiring has perfect continuity, the ground is good, and the bulb is functional, the BCM's internal driver circuit may have failed. The BCM will need to be replaced and reprogrammed by a Case IH dealer.