Case IH 3880 (F-3507-31) - ECU – Engine Control Module (ECM): ECU 12/24 volt actuator supply 4 is shorted to battery voltage

The engine computer is detecting unintended battery voltage on the circuit that powers actuator relay 3, pointing to a wiring short or a failed relay.

• VESTRUM CVX
• Axial-Flow 240 series
• Axial-Flow 5150
• Axial-Flow 6150
• Axial-Flow 7150
• Axial-Flow 7250
• Axial-Flow 8250
• Axial-Flow 9250
• Magnum CVT/CVX (265 to 400)
• Maxxum CVX (115 to 180)
• Optum CVX (250 to 340)
• Puma CVX / Puma X (140 to 260)
• Steiger / Quadtrac (370 to 620)
• Vestrum
• Patriot 3250
• Patriot 4450
• Farmlift 737
• Farmlift 742
• Case IH Graders
• Case IH Wheel Loaders

1. 1

   Identify the Circuit: Locate Actuator Relay 3 (High Side Actuator Relay) in the machine's main fuse/relay distribution box.

2. 2

   Harness Pin Check: Disconnect the harness from the Bosch MD1CE101 ECU. Using a multimeter, probe pins 5.11 and 6.34 on the harness side. Check for continuity to a 12V/24V battery power source.

3. 3

   Visual Inspection: Trace the wiring harness from the ECU to the relay block. Look for rubbed, chafed, or melted wire insulation that could be allowing the actuator supply wire to touch a live battery wire.

4. 4

   Relay Testing: Remove Actuator Relay 3 and test it for an internal short circuit. A fused relay contact can back-feed battery voltage into the ECU supply circuit.

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the negative battery cable to prevent electrical damage during testing.

2. 2

   Access the ECU

   Locate the Bosch MD1CE101 ECM (typically mounted on or near the engine block).

3. 3

   Disconnect and Isolate

   Disconnect the engine wiring harness connectors from the ECM.

4. 4

   Test the Relay

   Swap Actuator Relay 3 with a known good relay of the same type (e.g., the horn or work light relay). Reconnect the battery and ECU, then turn the key ON to see if the code changes to an open circuit or clears. If it clears, the relay was internally shorted.

5. 5

   Trace the Short

   If the relay is good, leave the ECU disconnected and use a multimeter to trace the wire from ECU pins 5.11/6.34 to the relay block.

6. 6

   Repair Wiring

   Once the short-to-battery is located in the harness (often at a rub point near the engine frame or relay box entry), cut out the damaged section of wire. Solder and heat-shrink a new section of wire to restore the circuit.

7. 7

   Reassemble and Clear Codes

   Reconnect all harness connectors and the battery. Use an Electronic Service Tool (EST) to clear the inactive fault codes. Run the engine to verify the code does not return.