John Deere 000627.01 – ECU: Injector Power Supply Malfunction

The Engine Control Unit (ECU) has detected a critical electrical issue with the power supply to the electronic fuel injectors. This can manifest as low voltage, high resistance across all injector circuits, or a short to ground in the ECU unswitched power. This condition prevents sufficient current from reaching the injectors, resulting in a loss of power, poor performance, or a failure to start.

• 410J
• 410K
• 410L
• 744K
• 210 Series
• 310 Series
• 5000 Series
• 6000 Series

1. 1

   Check battery voltage to ensure batteries are fully charged and providing adequate voltage to the ECU, as low system voltage can trigger this fault

2. 2

   With the ignition OFF, carefully inspect all electrical connectors related to the ECU and fuel injector harness for damage, corrosion, or loose connections

3. 3

   Connect the John Deere Service ADVISOR tool to read the codes and associated data to confirm the fault

4. 4

   Check for additional active fault codes that could be related to specific injector circuits or other ECU power supply issues

1. 1

   Disconnect power

   Turn the ignition OFF and disconnect the battery ground strap to ensure the system is de-energized before beginning repairs.

2. 2

   Inspect wiring harness

   Carefully inspect the fuel injector wiring harness for any signs of physical damage, such as chafing, cuts, or heat damage. Pay close attention to areas where the harness may rub against engine components.

3. 3

   Test circuit resistance

   If the fault is described as 'high resistance', use a multimeter and a detailed wiring diagram to check the resistance of the injector circuits.

4. 4

   Address short to ground

   If diagnosing an 'ECU Unswitched Power Short to Ground' fault (noted on models like the 744K), trace the unswitched power wire from the ECU to the power source, looking for any point where it may be contacting the chassis or other ground points.

5. 5

   Reprogram ECU

   If all physical connections are sound and wiring is intact, the ECU may need to be reprogrammed with the latest software by a qualified technician using Service ADVISOR.

6. 6

   Replace wiring harness

   If the wiring harness is found to be damaged during inspection or testing, replace it with a new OEM part.

7. 7

   Replace ECU

   If all other diagnostic steps fail to resolve the issue, the ECU itself may be faulty and require replacement as a last resort.