Case IH 3509-03 - BCM – BCM: Sensor Supply Voltage 1 (5V) - Voltage Above Normal, or Shorted to High Source.

The control module provides a regulated 5-volt reference signal to a specific bank of sensors (Bank 1). The "03" (FMI 3) failure mode indicates that the module is detecting a voltage significantly higher than 5V on this circuit—typically battery voltage (12V). This means the 5V reference wire is shorted to a B+ (battery positive) power source, which will cause all sensors sharing this 5V supply bank to fail or read out of range.

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1. 1

   Verify Fault Status: Use the Case IH Electronic Service Tool (EST) or the in-cab diagnostic display to check if the code is Active or Inactive.

2. 2

   Isolate the Sensors: Disconnect the sensors on the 5V Supply Bank 1 one at a time (e.g., accelerator pedal, hitch draft pins). If disconnecting a specific sensor causes the fault code to change from 'Shorted to High Source' to an open circuit/inactive state, that specific sensor has an internal short.

3. 3

   Voltage Test: Turn the key ON (engine OFF). Use a digital multimeter to measure the voltage at the 5V supply pin on a disconnected sensor harness. If it reads ~12V, the short to B+ is confirmed.

4. 4

   Harness Inspection: Visually inspect the cab and chassis wiring harnesses for chafing, rubbing, or pinched wires, particularly near cab pass-throughs, moving linkages, and tight bends where the 5V wire could rub against a 12V power wire.

1. 1

   Power Down

   Turn the ignition OFF and disconnect the battery ground cable to prevent module damage during testing.

2. 2

   Isolate the Harness

   Disconnect the main harness connectors at the BCM and unplug all sensors on the affected 5V reference circuit.

3. 3

   Test for Continuity

   Using a multimeter, test for continuity between the 5V supply wire pin at the BCM connector and any 12V power pins/wires in the harness.

4. 4

   Repair the Harness

   If continuity (a short) is found, trace the harness to locate the damaged section. Repair the wires using OEM-approved splice connectors and heat shrink, or replace that section of the harness.

5. 5

   Test the BCM

   If the harness tests perfectly fine and no sensors are internally shorted, the short to power may be internal to the BCM itself. Reconnect the battery and the BCM (leaving sensors unplugged). Turn the key ON and probe the 5V output pin at the BCM. If it outputs 12V, the BCM has an internal short and must be replaced.

6. 6

   Reassembly and Clearing

   Reconnect all sensors and modules. Reconnect the battery. Use the Case IH EST to clear the inactive fault codes. Cycle the key and let the machine idle for 1 minute to verify the repair.