Case IH F-1443-03 - ECU – Engine Control Unit (ECU): Fuel metering unit is shorted to battery voltage at the low side.

The control module is monitoring the signal circuit for the fuel metering unit (often designated as component Y-9000 or Y-011) and has detected a short circuit to a voltage source (battery voltage) on the low side driver circuit.

• MAGNUM AFS Connect
• Case IH 240 Series Combines
• Case IH Farmall 40, 45, and 50 Tractors
• Case IH Workmaster 50
• Case IH Magnum Tractors (MX210, MX230, MX255, MX285)
• Case N-Series TLBs (Tractor Loader Backhoes)

1. 1

   Verify active faults using the Electronic Service Tool (EST) or PT-Box Tool to determine if the issue is an intermittent electrical connection.

2. 2

   Check for related codes indicating open loads, over-temperature, or intermittent connections on the fuel metering unit (e.g., DTC 4155, 5255, 7555, 8355) or maximum rail pressure exceeded (DTC 1D85 / SPN 7557).

3. 3

   Inspect the wiring harness and connectors between the ECU and the fuel metering unit for chafed wires, melted insulation, or water ingress.

4. 4

   Disconnect the fuel metering unit and use a multimeter to test the low side driver circuit for voltage. Battery voltage on the ground/low side wire indicates a shorted harness.

5. 5

   Check the internal resistance of the fuel metering unit solenoid to ensure it has not failed internally and shorted out.

1. 1

   Disconnect Power

   Turn off the machine and disconnect the battery to prevent ECU damage during electrical testing and repair.

2. 2

   Repair the Harness (If Applicable)

   If your multimeter testing in the diagnostic phase revealed a short to battery voltage in the wiring harness, trace the harness back to the ECU. Repair or replace the damaged section of the wiring harness.

3. 3

   Replace the Fuel Metering Unit (If Applicable)

   If the wiring harness tests perfectly fine, the short is likely internal to the fuel metering unit itself. Locate the fuel metering unit (typically mounted directly to the Bosch high-pressure fuel injection pump). Clean the area thoroughly to prevent dirt from entering the fuel system. Disconnect the electrical connector. Remove the mounting screws and pull the metering unit out of the pump housing. Lubricate the O-rings on the new fuel metering unit with clean diesel fuel and install it into the pump. Torque the fasteners to OEM spec.

4. 4

   Clear Codes and Test

   Reconnect the battery. Connect the EST, clear the fault codes, and start the engine. Monitor the actual vs. desired fuel rail pressure to ensure the new unit is regulating fuel flow correctly.