Case IH 520326-06 - BCM – BCM: LIN Bus A - short circuit to ground

The communication wire for Bus A is making direct contact with the machine's chassis or a ground circuit, pulling the voltage down and preventing data transmission.

• MAGNUM AFS Connect
• Steiger AFS Connect

1. 1

   Inspect the wiring harness associated with LIN Bus A for obvious signs of chafing, rubbing, or pinched wires against the tractor's metal chassis.

2. 2

   Disconnect the devices on LIN Bus A one at a time to isolate the short. If the short-to-ground fault changes to an open circuit or clears, the internally shorted component you just disconnected is the culprit.

3. 3

   Disconnect the LIN Bus A connector at the BCM. Use a digital multimeter to measure continuity between the LIN Bus A signal wire and a known good chassis ground. If there is continuity, the short is in the wiring harness.

4. 4

   Inspect the BCM connectors and peripheral device connectors for water ingress, bent pins, or corrosion that could bridge the LIN circuit to a ground pin.

1. 1

   Power Down

   Turn off the machine and disconnect the battery power using the battery isolator switch to prevent electrical damage during testing.

2. 2

   Access the BCM

   Locate the Body Control Module (BCM) within the cab/electrical routing area.

3. 3

   Disconnect and Trace

   Disconnect the harness containing LIN Bus A. Using your multimeter, trace the circuit along the harness routing, paying special attention to areas where the harness passes through bulkheads, tight bends, or near moving parts.

4. 4

   Repair the Wiring

   Once the shorted section of the wire is found, cut out the damaged section. Splice in a new section of wire of the same gauge, solder the connection, and seal it with marine-grade heat shrink tubing to prevent moisture ingress.

5. 5

   Component Replacement (If Applicable)

   If the wiring is intact but a specific switch or actuator on the LIN bus is internally shorted to ground, replace that specific component.

6. 6

   Reassembly and Testing

   Reconnect all modules and the battery isolator. Turn the key on, clear the inactive fault codes via the AFS Pro monitor, and verify that code 520326-06 does not return.