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).