Case IH 520446-06 - BCM – BCM: Roof mounted headlamp low beam right - short circuit to ground.

The control module has detected that the voltage intended for the right-side roof-mounted low beam headlamp is finding a premature path to ground. This typically means the power wire is touching the metal chassis (due to chafing or a pinch), the connector is melted/corroded, or the headlamp assembly itself has an internal short. In the J1939 standard, the "-06" FMI (Failure Mode Identifier) designates a "Current above normal or grounded circuit".

• MAGNUM AFS Connect
• Magnum (180, 200, 220, 240, 250, 280, 310, 340, 380)
• Steiger
• Puma
• Maxxum
• Axial-Flow (7140, 7230, 8230, 8240, 9230, 9240)
• Cotton Pickers
• CX/MC series
• AFS Connect Magnum Tier 4B

1. 1

   Visual Inspection: Inspect the right roof-mounted headlamp assembly for physical damage, water intrusion, or a melted connector.

2. 2

   Component Isolation: Disconnect the right roof headlamp. Turn the lights on and check the active fault codes using the CNH EST (Electronic Service Tool). If the code changes from "short to ground" to an "open circuit" (often FMI -05), the short is internal to the headlamp assembly.

3. 3

   Harness Inspection: If the code remains a "short to ground" with the lamp unplugged, the short is in the wiring harness. Trace the wiring from the roof headlamp back to the BCM. Pay special attention to areas where the harness routes through the cab roof structure or down the A-pillar, as vibration often causes wire chafing.

4. 4

   Continuity Test: Disconnect the headlamp harness at the BCM. Use a digital multimeter to test for continuity between the headlamp power supply pin and a known good chassis ground. If continuity exists, the wire is shorted to the frame.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the negative battery cable to prevent further electrical damage or accidental shorts during repair.

2. 2

   Address the Short

   If the harness is damaged: Locate the chafed or pinched section of the wire. Cut out the damaged section and repair it using weather-resistant, heat-shrink butt connectors, or replace that specific harness section. Secure the harness with zip ties to prevent future rubbing. If the headlamp is internally shorted: Unbolt the right roof headlamp from its mounting bracket and install a replacement assembly.

3. 3

   Reassembly

   Reconnect the headlamp and the battery.

4. 4

   Clear Codes

   Connect the CNH EST diagnostic tool to clear the stored BCM fault codes.

5. 5

   Verify Operation

   Turn on the low beams and verify the right roof headlamp illuminates without tripping the fault code again.