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  • P0628 Low Voltage Detected At The Fuel Lift Pump

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    P0628 LOW VOLTAGE DETECTED AT THE FUEL LIFT PUMP

    When Monitored and Set Condition:

    When Monitored: While the key is on.
    Set Condition: The voltage detected on the Fuel Lift Pump is above a calibrated value for a calibrated amount
    on time.

    POSSIBLE CAUSES

    • LOOSE CONNECTION
    • GROUND CIRCUIT OPEN
    • LIFT PUMP SHORTED TO VOLTAGE
    • LIFT PUMP
    • ECM

    DIAGNOSTIC PROCEDURE

    1. With the DRBIII®, in system test actuate the lift pump. Does the lift pump run?
      Yes --> Go To 2
      No --> Go To 3
    2. Lift pump actuation still running. While the lift pump is running, wiggle the wiring harness and connectors throughout the circuit. Does this interrupt the pump operation?
      Yes --> Repair the loose connection. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Go To 3
    3. Disconnect the ECM harness connectors.
      NOTE: Check connectors - Clean/repair as necessary.
      Measure the resistance of the lift pump (K62) supply circuit between the ECM harness connector and the lift pump harness connector. Is the resistance less than 1 Ohms?
      Yes --> Go To 4
      No --> Test Complete.
    4. Measure the resistance of the ground circuit between the lift pump connector and battery negative. Is the resistance less than 1 Ohms?
      Yes --> Go To 5
      No --> Repair the open ground circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    5. Measure the voltage between the supply and ground circuits of the lift pump connector. Is the voltage greater than 1 volt?
      Yes --> Repair the lift pump circuits shorted to voltage. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Go To 6
    6. Reconnect the ECM harness connectors. Connect a jumper wire between the (K62) supply circuit and ground circuit of the lift pump harness connector. Turn the ignition on. With the DRBIII®, read DTCs. Did DTC P0628 set?
      Yes --> Replace the lift pump. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Replace the ECM. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).

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