Case IH 520326-03 - BCM – Section Control ECU / Body Control Module (BCM): Select Right, Voltage above normal, or shorted to high source

The Local Interconnect Network (LIN) single-wire communication line is constantly receiving battery voltage (approx. 12–14V), which completely halts communication on that bus.

• MAGNUM AFS Connect
• Precision Air Carts 2230
• Precision Air Carts 2280
• Precision Air Carts 2330
• Precision Air Carts 3380
• Precision Air Carts 3430
• Magnum
• Steiger
• Optum
• Puma

1. 1

   Connect a battery tender to maintain system voltage, as LIN bus diagnostics rely on reading voltage drops from 12V down to 1V.

2. 2

   Measure LIN Bus A wire voltage using a multimeter or oscilloscope. A short to B+ will show a flat line at battery voltage (12V+) with no sync breaks.

3. 3

   Isolate the short by disconnecting LIN slave modules (switches, sensors, wiper motors) one by one. If voltage drops and communication restores, the disconnected module has an internal short.

4. 4

   If all slave modules and the BCM are disconnected and the wire still reads 12V, inspect the wiring harness, intermediate connectors, and joint connectors for corrosion, moisture, or pinched wires.

1. 1

   Power down system

   Turn the ignition off and disconnect the negative battery terminal. Wait at least 90 seconds if the equipment has any SRS/airbag systems.

2. 2

   Repair wiring harness

   If the wiring is at fault, locate the chafed insulation or pinched wire where the LIN bus line is contacting a 12V power supply line. Splice and solder the damaged section, and seal it with heat-shrink tubing.

3. 3

   Replace faulty module

   If diagnostics isolated the short to a specific slave module or the BCM itself, unbolt the faulty module, disconnect the harness, and install the replacement unit.

4. 4

   Reassemble and reconnect

   Plug in all previously disconnected ECU and slave module connectors. Reconnect the negative battery terminal.

5. 5

   Clear codes and verify

   Turn the ignition to the 'ON' position. Use a diagnostic scan tool to clear active/pending codes. Cycle the ignition and verify that the LIN bus voltage is toggling normally and the fault does not return.