John Deere 627 – ECU: Injector Currents Out of Specification

The Engine Control Unit (ECU) has detected that the electrical current for all fuel injectors is outside of the expected range. Specifically, the injector pull-in current is too low or the injector hold-in current is incorrect. This is most commonly caused by high resistance in the injector electrical circuit, such as a degraded wiring harness, rather than a simultaneous failure of all injectors.

• 8120
• 8220
• 8320
• 8420
• 8520
• 9020T Series
• 160D Excavator

1. 1

   Visually inspect the full length of the engine wiring harness from the ECU to the cylinder head for chafing, melting, corrosion, or pinched wires

2. 2

   Disconnect and inspect the main engine harness connector at the cylinder head for bent or corroded pins, moisture intrusion, or loose connections

3. 3

   Remove the valve cover to inspect the internal injector wiring harness for brittle, flaking, or oil-saturated insulation (a common failure point)

4. 4

   Perform resistance and continuity tests on the injector harness using a multimeter: disconnect the harness from the ECU and all injectors, check for continuity (no open circuits), high resistance (healthy wires are typically < 1 ohm), and short circuits between wires or to ground

1. 1

   Isolate the faulty component

   Based on diagnostic checks, determine if the high resistance fault lies in the main engine harness, the internal harness under the valve cover, or the ECU (least likely).

2. 2

   Repair or replace wiring harness

   Repair damaged wires on the external engine harness. If the internal injector harness under the valve cover shows signs of degradation, replace it entirely, as this is a frequent solution for this fault code.

3. 3

   Test fuel injectors

   If the harness is confirmed to be in good condition, test the injectors for correct resistance. A faulty injector will typically show a resistance value significantly different from the others.

4. 4

   Clear codes and verify repair

   Reconnect all connectors, clear the diagnostic trouble codes using a service tool, and start the engine to ensure the fault code does not reappear.