P0629 HIGH VOLTAGE DETECTED AT THE FUEL LIFT PUMP

When Monitored and Set Condition:

When Monitored: While the key is on.
Set Condition: The commanded signal to the lift pump does not match the feedback signal from the lift pump.

POSSIBLE CAUSES

• LOOSE CONNECTION
• (K62) SUPPLY CIRCUIT SHORTED TO VOLTAGE
• (K62) SUPPLY CIRCUIT SHORTED
• 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 5
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.
   No --> Go To 3
3. Disconnect the ECM harness connectors.
   NOTE: Check connectors - Clean/repair as necessary.
   Measure the resistance between the lift pump (K62) supply circuit of the lift pump connector and battery negative. Is the resistance greater than 100k Ohms?
   Yes --> Go To 4
   No --> Repair the (K62) supply circuit shorted to voltage.
4. Measure the resistance between the lift pump (K62) supply circuit and all other circuits in the ECM harness connectors. Is the resistance greater than 100k Ohms?
   Yes --> Go To 5
   No --> Repair the (K62) supply circuit shorted to another circuit.
5. Reconnect the disconnected Lift pump harness connector. Reconnect the ECM harness connectors. Turn the ignition on. With the DRBIII®, read DTCs while disconnecting the lift pump. Did P0628 set?
   Yes --> Replace the lift pump.
   No --> Replace the ECM