Case IH 520329-06 - BCM – BCM: CAN Bus A - short circuit to ground (Curto com o terra)

CAN Bus A has a short circuit to ground. This means either the CAN High or CAN Low communication wire is physically touching a ground source (such as the tractor's metal chassis), pulling the bus voltage down to 0V and disrupting or shutting down all communication across that specific network branch.

• MAGNUM AFS Connect
• Case IH Magnum AFS Connect (Models 180, 200, 220, 240, 250, 280, 310, 340, 380, and 400)
• Case IH Steiger AFS Connect

1. 1

   Turn off the ignition, remove the key, and ensure the machine is parked safely.

2. 2

   Inspect the CAN Bus A wiring harness and connectors for physical damage, chafing, frayed insulation, or moisture/corrosion. Pay special attention to areas where the harness routes near the chassis or moving parts.

3. 3

   With the ignition ON, use a multimeter to measure the voltage on the CAN High and CAN Low pins at the BCM connector. If the line is shorted to ground, the oscilloscope or multimeter trace will flatline at or near 0V.

4. 4

   With the ignition OFF and the battery disconnected, measure the resistance between the CAN Bus A pins and chassis ground. A low resistance reading confirms a direct short to ground.

5. 5

   Because a short on the CAN bus takes down the whole branch, disconnect modules on CAN Bus A one by one. If the short-to-ground reading disappears after unplugging a specific module, that module is internally shorted. If the short remains with all modules unplugged, the fault is in the wiring harness.

1. 1

   Disconnect Power

   Disconnect the battery via the battery isolator to prevent electrical damage while working on the network.

2. 2

   Trace the Fault

   Using the machine's electrical wiring diagram, trace the CAN Bus A lines from the BCM to the rest of the network.

3. 3

   Isolate and Repair Wiring

   Once the exact point of the short circuit is located (e.g., a chafed wire touching the frame), repair the damaged wire by splicing it and sealing it with heat-shrink tubing. If the damage is extensive, replace that section of the harness.

4. 4

   Replace Module (If Applicable)

   If the isolation test proved that a module (such as the BCM itself) is internally shorted to ground, remove and replace the module.

5. 5

   Reassemble and Reconnect

   Reconnect all network nodes, connectors, and finally the battery.

6. 6

   Clear Codes and Test

   Turn the ignition ON. Use the manufacturer-approved diagnostic scan tool (e.g., EST) to clear the 520329-06 fault code. Perform a functional test of the tractor to ensure CAN Bus A communication is fully restored and the code does not return. Note: If the BCM is replaced, the new module must be initialized and programmed with the vehicle's specific configuration files using the diagnostic tool.