Case IH 3509-06 - BCM – BCM: Sensor regulated power (5V) - short circuit to ground

The 5-volt reference circuit (VREF 1) that supplies power to various sensors has shorted to a ground source. When this happens, the 5V supply is pulled down to 0V, causing all sensors on that specific circuit to lose power and stop reporting data to the control module.

• MAGNUM AFS Connect
• Case IH Magnum AFS Connect (Models 180, 200, 220, 240, 250, 280, 310, 340, 380)
• Case IH Steiger AFS Connect
• Case IH Puma (Models 200, 215, 230)

1. 1

   Sensor Isolation Test: Identify all sensors powered by the BCM's 5V Supply 1 circuit. Unplug these sensors one at a time while monitoring the 5V circuit with a multimeter (or monitoring the fault code status via the Electronic Service Tool). If the 5V reference voltage returns to normal when a specific sensor is unplugged, that sensor is internally shorted.

2. 2

   Harness Inspection: If all sensors are unplugged and the short to ground is still present, inspect the wiring harness between the BCM and the sensors. Look for chafed insulation, pinched wires against the chassis, or melted wire loom.

3. 3

   Connector Check: Inspect the BCM connectors and sensor connectors for water ingress, corrosion, or bent pins that could be bridging the 5V pin to a ground pin.

4. 4

   BCM Output Test: Disconnect the sensor harness directly at the BCM. Measure the 5V output pin on the BCM. If the BCM does not output 5V with the harness disconnected, the BCM is internally shorted or damaged.

1. 1

   Power Down

   Turn off the ignition and disconnect the battery isolator switch to prevent electrical spikes during repair.

2. 2

   Locate the Short

   Using the diagnostic checks above, pinpoint the source of the short circuit to ground.

3. 3

   Repair the Harness (If Applicable)

   If a wire is chafed and touching the chassis, cut out the damaged section, solder in a new piece of wire, and seal it with dual-wall heat shrink. Reroute the harness away from sharp edges or high-heat sources.

4. 4

   Replace the Sensor (If Applicable)

   If a sensor was found to be internally shorted during the isolation test, replace the sensor and ensure the connector is clean and packed with dielectric grease if required by the OEM.

5. 5

   Replace the BCM (If Applicable)

   If the BCM itself is the point of failure, remove the mounting hardware and connectors, install the new BCM, and ensure all connections are seated securely.

6. 6

   Reprogramming

   If the BCM is replaced, the new module will need to be flashed/programmed with the correct software dataset for the specific tractor configuration using the Case IH Electronic Service Tool (EST).

7. 7

   Clear Codes

   Reconnect the battery, turn the key on, and use the EST to clear code 3509-06. Verify that the 5V reference voltage is stable and the code does not return.