Case IH 520331-06 - BCM – BCM: CAN Bus C - short circuit to ground

The CAN Bus C network is experiencing a short circuit to ground on its communication lines (CAN_H or CAN_L). This pulls the network voltage down, disrupting the data transmission between the control modules that rely on this specific bus.

• MAGNUM AFS Connect
• Case IH Magnum AFS Connect Series
• Case IH Steiger AFS Connect Series

1. 1

   Visual Harness Inspection: Inspect the CAN Bus C wiring harness for physical damage, chafing, or pinched wires that could cause the bare wire to touch the chassis ground.

2. 2

   Flex Test: Flex the wiring harnesses while observing the diagnostic monitor to uncover intermittent shorts to ground in the wiring.

3. 3

   Resistance Testing: With the battery disconnected, test the CAN Bus C for proper resistance. A healthy CAN bus with two terminating resistors (one external plugged into the end of the bus, and one internal in a controller) should read approximately 60 ohms. A reading significantly lower or showing continuity to ground confirms the short.

4. 4

   Module Isolation: Because a short to ground can be caused by a failed module pulling the bus down internally, disconnect the modules on CAN Bus C one by one. If the short to ground disappears when a specific module is unplugged, that module is the root cause.

1. 1

   Isolate the Power

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

2. 2

   Locate the Short

   Using a multimeter, trace the CAN Bus C circuit to locate the exact point of the short to ground (either a damaged wire or a faulty module).

3. 3

   Repair the Wiring

   If the harness is damaged, repair the affected wiring segment using OEM-approved splicing methods, or replace the damaged harness section entirely. Ensure the repaired section is properly shielded and routed away from sharp chassis edges.

4. 4

   Replace Faulty Components

   If the short is internal to a module (such as the BCM or a connected smart sensor), replace the faulty module.

5. 5

   Re-test and Clear Codes

   Reconnect the battery, turn the ignition on, and use the Case IH Electronic Service Tool to clear the inactive fault codes. Operate the machine and monitor the display to ensure the CAN Bus C readings are normal and the fault does not return.