Case IH 518888-03 - BCM – BCM: Ambient color illumination driver - short circuit to B+

The control circuit responsible for powering the cab's interior ambient color lighting has shorted to battery voltage (B+). The system is detecting 12V power on the driver circuit when it should not be present, which disables the circuit to protect the module.

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

1. 1

   Isolate the Component: Disconnect the ambient color lighting strips/assemblies in the cab. Turn the key on and check if the fault code changes from an '03' (Short to B+) to an '05' (Open Circuit). If the code changes, the short is internal to the lighting component itself.

2. 2

   Harness Inspection: Inspect the cab roof and interior trim wiring harness leading to the ambient lights. Look for pinched wires, chafing, or exposed copper that might be touching a constant 12V power source.

3. 3

   Multimeter Testing: With the battery disconnected, use a multimeter to test the ambient lighting driver circuit wire for continuity to battery positive (B+).

4. 4

   BCM Connector Check: Inspect the connectors at the Body Control Module for water ingress, corrosion, or bent pins, which can bridge power across terminals.

1. 1

   Power Down

   Turn off the tractor ignition and disconnect the battery to prevent further electrical damage.

2. 2

   Access the Circuit

   Remove the necessary cab interior trim panels to access the ambient lighting LED strips and their sub-harnesses.

3. 3

   Repair Wiring

   If the diagnostic checks revealed a pinched or chafed wire shorting to a power wire, repair the damaged section using heat-shrink connectors, or replace that section of the cab harness.

4. 4

   Replace Component

   If the ambient lighting unit was internally shorted, remove the faulty LED strip/housing and install the replacement unit.

5. 5

   BCM Replacement (Worst Case)

   If the wiring and lighting components test perfectly fine but the circuit still outputs a constant short to B+, the BCM has an internal driver failure. Replace the BCM and flash it with the correct software using the Electronic Service Tool (EST).

6. 6

   Clear and Test

   Reconnect the battery. Use the AFS Pro 1200 display or a diagnostic tool to clear the inactive fault codes. Turn on the ambient lighting to verify the repair and ensure the code does not return.