John Deere 1075 – RCU: Fuel Transfer Pump Unexpectedly ON

The fuel transfer pump (cc# 188) is operating even though it has not been commanded to do so by the right power module. This indicates an unexpected activation of the component. The control module has detected voltage on the fuel transfer pump's signal or control circuit when there should be none (FMI 03: Voltage Above Normal, or Shorted to High Source). The underlying condition is an electrical short to a power source somewhere in the circuit between the Right Power Module and the fuel transfer pump, causing the pump to run continuously or at inappropriate times.

• 9560 STS
• 9650 STS
• 9660 STS
• 9670 STS
• 9750 STS
• 9770 STS
• 9870 STS
• S660
• S670
• S680
• S685
• S690

1. 1

   Verify that the RCU 1075.03 fault code is currently active, as intermittent issues may not be present at the time of testing.

2. 2

   Visually inspect the wiring harness between the Right Power Module, associated relays, and the fuel transfer pump for chafed or melted insulation, corrosion on connectors, or pinched wires.

3. 3

   With the pump disconnected, use a multimeter to test the signal wire in the harness for voltage. There should be no voltage present when the pump is not commanded ON; voltage indicates a short to another wire.

4. 4

   Check the integrity of all related fuses in the power distribution center (e.g., fuse F26 on S680 and S690 models).

1. 1

   Disconnect power

   Disconnect the machine's battery before working on the electrical system for safety.

2. 2

   Isolate the component

   Disconnect the electrical connector at the fuel transfer pump to determine if the fault is internal to the pump or in the wiring.

3. 3

   Test the circuit

   Turn the ignition on (without starting the engine) and clear the fault codes. Check if the RCU 1075.03 fault code returns with the pump disconnected. If the fault code does not return, the issue is an internal fault in the fuel transfer pump causing a voltage feedback loop, and the pump must be replaced. If the fault code does return, the signal/control wire is shorted to a power wire in the harness or control module.

4. 4

   Repair wiring

   If a short in the harness is identified, carefully separate the shorted wires, repair any breaks, and re-insulate them properly. If the damage is extensive, replace that section of the harness.

5. 5

   Re-assemble and test

   Reconnect all components and the battery. Start the machine and verify that the fault code does not reappear and that the fuel transfer pump operates only when commanded.