Case IH 2653-03 - BCM – Body Control Module (BCM): Headlamp low beam left #1 - Voltage above Normal, or Shorted to High Source

The control module is detecting battery voltage (B+) on the left low beam circuit when it shouldn't be, or the voltage is higher than the expected operating range. This condition is typically caused by the power feed wire shorting directly to another live power wire in the harness, an internal short within the headlamp assembly/LED module, or an internal failure within the control module itself keeping the circuit stuck "high".

• MAGNUM AFS Connect
• Magnum
• Puma
• Maxxum
• Steiger

1. 1

   Disconnect the left headlamp assembly connector and check if the fault code changes from FMI 3 to FMI 5 (Open Circuit), which indicates the short is internal to the headlamp assembly or bulb.

2. 2

   Inspect the headlamp connector and the BCM output pins for melted plastic, water intrusion, or bent pins that could be bridging circuits.

3. 3

   With the headlight switch OFF and headlamp disconnected, use a digital multimeter to check the left low beam power wire for continuity to other power wires or the battery positive terminal.

4. 4

   Test the specific BCM output pin for the left low beam. If it constantly outputs 12V/24V even when the lighting system is completely turned off and the harness is isolated, the BCM has an internal short.

1. 1

   Power Down

   Turn off the machine and engage the battery disconnect switch to prevent electrical spikes.

2. 2

   Inspect and Clean

   Disconnect the left headlamp. Clean the contacts with electrical contact cleaner. If the connector is melted or damaged, splice in a new connector pigtail using closed-barrel butt connectors and weather-resistant heat shrink tubing.

3. 3

   Replace the Headlamp/Bulb

   If the diagnostic checks isolated the short to the headlamp, replace the faulty halogen bulb. If the tractor is equipped with sealed LED headlamp modules, the entire left headlamp assembly must be replaced.

4. 4

   Repair the Harness

   If a harness short was found, trace the wiring back to the BCM. Look for pinch points, areas where the harness rubs against the frame, or melted insulation. Cut out the damaged section of the wire and solder/splice a new section of wire, sealing it with heat shrink.

5. 5

   Replace the BCM (Worst Case)

   If the BCM is internally shorted, remove the module and install a replacement. Note: A new BCM will likely require dealer programming/flashing to match the tractor's specific configuration.

6. 6

   Verify Repair

   Reconnect the battery, turn the ignition on, and clear the inactive fault codes using a diagnostic scan tool. Turn on the low beams to verify the left headlamp illuminates and the code does not return.