My new-to-me '03 235 HP 2500 with 107K threw a code today, out of the blue, a P 0628

which I understand to be a 'Fuel Pump Relay Circuit Low, or Fuel Lift Pump Control Circuit Low' problem. However, the truck runs FINE. No hiccups, stutters, or anything else. Should I replace the pump anyway? Is there anything else it could be? Any chance of engine damage in the interim?

 

This should get yo uall the info you need to be able to diagnose it!




Symptom:
P0628-LOW VOLTAGE DETECTED AT THE FUEL LIFT PUMP
When Monitored and Set Condition:
P0628-LOW VOLTAGE DETECTED AT THE FUEL LIFT PUMP
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
TEST ACTION APPLICABILITY
1 With the DRBIIIt, in system test actuate the lift pump.
Does the lift pump run?
All
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?
All
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?
All
Yes ! Go To 4
No ! Test Complete.
192
DRIVEABILITY - DIESEL

TEST ACTION APPLICABILITY
4 Measure the resistance of the ground circuit between the lift pump connector and
battery negative.
Is the resistance less than 1 Ohms?
All
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?
All
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 DRBIIIt, read DTCs.
Did DTC P0628 set?
All
Yes ! Replace the lift pump.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
No ! Replace the ECM.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
193
DRIVEABILITY - DIESEL
P0628-LOW VOLTAGE DETECTED AT THE FUEL LIFT PUMP — Continued