Case IH F-3508-31 - ECU – Engine Control Unit (ECU): Supply UB2 short circuit to battery failure

Actuator Supply 1 (a 12/24-volt supply line) is shorted to battery voltage.

• MAGNUM AFS Connect
• 240 Series Axial-Flow Combines
• Magnum AFS Connect Series
• Optum Series
• Puma Series
• Maxxum Series
• Steiger / Quadtrac Series
• Vestrum Series

1. 1

   Identify the affected circuit: Actuator Supply 1 (UB2) corresponds directly to pins 2.08, 4.03, and 4.19 on the Bosch MD1CE101 ECU connector.

2. 2

   Inspect the wiring harness leading to the ECU for any signs of chafing, melting, or pinched wires that could cause a short to a battery positive source.

3. 3

   Disconnect the ECU and use a multimeter to test the continuity of the actuator supply circuit (pins 2.08, 4.03, 4.19) to the battery positive terminal to confirm the short.

4. 4

   Check the individual actuators powered by this supply line for internal short circuits.

1. 1

   Disconnect battery

   Disconnect the machine's battery before performing any electrical repairs to prevent further module damage.

2. 2

   Inspect ECU connector pins

   Disconnect the main harness from the Bosch MD1CE101 ECU and inspect the connector pins (specifically 2.08, 4.03, and 4.19) for corrosion, bent pins, or internal shorting.

3. 3

   Trace and repair wiring harness

   Trace the wiring harness from the ECU to the engine actuators. If a short to battery voltage is found in the wiring harness, repair the damaged section of the wire or replace the affected harness segment.

4. 4

   Replace faulty actuator

   If an actuator is found to be internally shorted to battery voltage during your diagnostic checks, replace the faulty actuator.

5. 5

   Repair or replace ECU

   If the wiring harness and all actuators test fine, the ECU itself may have suffered an internal hardware failure (e.g., a defective internal transistor for supply UB2) and will require professional repair or replacement.

6. 6

   Reconnect and verify

   Reconnect all components, restore battery power, and clear the fault codes to verify the repair.