Case IH 520331-03 - BCM – BCM (Body Control Module): CAN Bus C - short circuit to B+ (Battery Positive)

This indicates that the CAN Bus C communication network has a short circuit to battery voltage (B+). When a CAN Bus line is shorted to power, the communication pathway is severed, preventing the modules on that specific bus from sending or receiving critical data.

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

1. 1

   Inspect the CAN Bus C wiring harness for any signs of chafing, rubbing, or melted insulation that could cause the wires to touch a power source.

2. 2

   Flex the wiring harnesses while observing the diagnostic monitor to uncover intermittent short circuits.

3. 3

   With the battery disconnected, measure the resistance across the CAN Bus C network. A healthy, typical 2-terminator CAN Bus should read approximately 60 ohms.

4. 4

   Turn the ignition switch to the ON position. Back-probe the CAN Bus C connector pins to chassis ground. If the voltage reads significantly higher than the standard CAN operating voltage (e.g., reading full battery voltage or > 4.5V), the short to B+ is confirmed in the harness.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the battery isolator to prevent electrical damage during repair.

2. 2

   Isolate the Short

   Disconnect modules on CAN Bus C one at a time (including the BCM and engine/emissions controllers) while monitoring the voltage/resistance on the bus lines.

3. 3

   Repair the Harness

   If the short disappears when a specific section of the harness is isolated, locate the damaged wire in that section. Splice and repair the wire using OEM-approved heat-shrink connectors, or replace that section of the harness.

4. 4

   Module Replacement

   If the wiring harness tests perfectly fine and the short is isolated to the BCM itself (internal short to power), the Body Control Module must be replaced.

5. 5

   Clear Codes

   Reconnect all components, restore battery power, and use the Case IH diagnostic tool to clear the fault code and verify that CAN Bus C communication is restored.