John Deere 1075.06 – ECU: Low Pressure Fuel Pump Circuit Has Low Resistance

The Engine Control Unit (ECU) has detected abnormally low electrical resistance in the low-pressure fuel pump (lift pump) control circuit. This condition is typically caused by a short circuit to ground in the wiring harness or an internal short within the electric fuel pump itself. When this fault is active, the ECU cannot properly energize the lift pump relay, which can lead to low fuel pressure, hard starting, or the engine entering a derated (limp) mode.

• 5085E
• 5090E
• 5090EL
• 5100E
• 5085M
• 5100M
• 5100MH
• 5100ML
• 5115ML
• 5090M
• 5115M
• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• PowerTech E 4.5L
• PowerTech E 6.8L
• PowerTech E 9.0L
• PowerTech Plus 4.5L
• PowerTech Plus 6.8L
• PowerTech Plus 9.0L
• 310SL
• 210K EP
• 210LJ
• 748H
• 540H
• 548H
• 8310RT
• 8335RT
• 8360RT
• 6010 series
• 6020 series
• 7020 series
• 9660 STS
• 9760 STS

1. 1

   Check for intermittent faults by clearing the code and operating the machine to see if the DTC periodically goes away or returns immediately

2. 2

   Inspect the low-pressure fuel pump wiring harness and the fuel lift pump relay harness for exposed wires, chafing, or a short to ground

3. 3

   Test the fuel lift pump relay (often designated as K17 or K25) for internal shorts or above-normal operating voltage

4. 4

   Test the fuel pump resistance by disconnecting the electric low-pressure fuel pump and measuring its internal resistance to check for an internal short

1. 1

   Disconnect Power

   Turn off the machine and disconnect the battery to prevent electrical spikes.

2. 2

   Examine Connectors

   Disconnect the harness at the low-pressure fuel pump and the ECU. Inspect the connector pins for corrosion, moisture, or melting. Use a connector adapter test kit (like John Deere JT07328) to avoid damaging the terminals.

3. 3

   Repair Wiring

   If a short to ground is found in the harness, repair the damaged section of the wire or replace the specific jumper harness.

4. 4

   Replace the Relay

   If the lift pump relay is shorted, replace the relay and re-test the circuit.

5. 5

   Replace the Fuel Pump

   If the wiring and relay are intact, the low resistance is internal to the pump. Remove the fuel lines and electrical connector from the low-pressure lift pump, unbolt it from its mounting bracket, and install the replacement pump.

6. 6

   Prime the System and Clear Codes

   Reconnect the battery, turn the key to the ON position to allow the new lift pump to prime the fuel system, and clear the ECU codes. Start the engine and verify the code does not return.