Case IH 520578-03 - BCM – BCM: Battery isolator reset - short circuit to B+

An unwanted electrical path exists between the battery isolator reset circuit and a battery voltage (B+) source. The controller logic is detecting power on a circuit that should currently be disabled or grounded.

• MAGNUM AFS Connect
• Magnum AFS Connect 250
• Magnum AFS Connect 280
• Magnum AFS Connect 310
• Magnum AFS Connect 340
• Magnum AFS Connect 380
• Magnum AFS Connect 400
• Steiger
• Puma

1. 1

   Inspect the wiring harness running between the Body Control Module (BCM) and the battery isolator relay/switch for chafed wires where the reset circuit might be rubbing against a constant power wire.

2. 2

   Disconnect the electrical connectors at the BCM and the battery isolator switch and inspect for bent pins, corrosion, or moisture ingress that could be bridging a B+ terminal to the reset circuit pin.

3. 3

   With the connectors unplugged, use a multimeter to check for continuity between the battery isolator reset wire and a known B+ power source.

4. 4

   Test the battery isolator switch and relay for internal shorts.

1. 1

   Power Down

   Turn off the tractor and manually disconnect the main negative battery cable to ensure safety.

2. 2

   Disconnect Components

   Disconnect the electrical connector at the battery isolator switch/relay.

3. 3

   Repair Wiring

   If your diagnostic multimeter tests revealed a short to power in the wiring harness, trace the harness to find the damaged section. Splice and repair the wire using OEM-approved heat-shrink connectors, or replace the affected harness section.

4. 4

   Replace Isolator Switch/Relay

   If the wiring tests good but the isolator switch/relay is internally shorted to B+, unbolt the faulty switch/relay from its mounting bracket and install the replacement part. Reconnect the electrical connector.

5. 5

   BCM Replacement

   If the wiring harness and the isolator switch both test perfectly fine, the internal circuitry of the BCM may have failed, causing it to falsely read a short to B+. The BCM will need to be replaced and flashed with the correct software for your specific tractor PIN.

6. 6

   Clear Codes

   Reconnect the battery, turn the key on, and use the diagnostic menu on the AFS Pro monitor (or an electronic service tool) to clear the fault code and verify the repair.