p0628 low voltage detected at the fuel lift pump

[98whitelightnin]

Friend called me saying his early 04 truck died and hes getting p0628 code. Does this mean a bad connection or bad lift pump? Believe his is still on the block.

[AH64ID]

P0628-LOW VOLTAGE DETECTED AT THE FUEL LIFT PUMP (CONTINUED)For the Engine circuit diagram (Refer to 9 - ENGINE - SCHEMATICS AND DIAGRAMS)For a complete wiring diagram Refer to Section 8W.² When Monitored:While the key is on.² Set Condition:The commanded signal to the fuel lift pump relay does not match the feedback signal from the fuel lift pumprelay.Possible CausesWIRING HARNESSFUEL LIFT PUMP RELAYFUEL LIFT PUMP RELAY DRIVER CIRCUIT SHORTED TO EXTERNAL VOLTAGEFUEL LIFT PUMP RELAY DRIVER CIRCUIT OPENFUEL LIFT PUMP RELAY GROUND CIRCUIT OPENFUEL LIFT PUMP RELAY GROUND CIRCUIT SHORTED TO EXTERNAL VOLTAGEECMAlways perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -DIAGNOSIS AND TESTING)Diagnostic Test1. LIFT PUMP RUNSRemove the cover to the PDC.Turn the ignition on, engine off.With the scan tool, in system test actuate the lift pump relay.Does the fuel lift pump relay click when the lift pump is actuated?Yes >> Test complete.Perform Intermittent Condition test. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)No >> Go To 22. LIFT PUMP RELAY DOES NOT CLICKTurn Ignition off.Remove the lift pump relay from the PDC.Turn the ignition on.Connect one end of an incandescent test light to battery negative.Connect the other end of the test light to the relay driver pin in the PDC.With the scan tool, in system test actuate the lift pump relay.Does the test light illuminate brightly?Yes >> Go To 3No >> Go To 53. FUEL LIFT PUMP GROUND CIRCUIT OPENConnect one end of an incandescent test light to battery postive.Connect the other end of the test light to the relay ground pin in the PDC.Is the resistance less than 1 Ohms?Yes >> Go To 4No >> Repair the open ground circuit.Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONICCONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)4. LIFT PUMP RELAYInstall a know good relay in place of the fuel lift pump relay.With the scan tool, in system test actuate the lift pump relay.Does the fuel lift pump relay click when the lift pump is actuated?No >> Go To 5Yes >> Replace the lift pump relay.Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONICCONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)5. FUEL LIFT PUMP DRIVER CIRCUIT OPENTurn Ignition off.Disconnect the ECM connectors.NOTE: Check connectors - Clean/repair as necessary.Using an ohmmeter, measure the resistance of the lift pump relay driver wire between the ECM connector and thePDC.Is the resistance less than 10 Ohms?No >> Repair the Fuel lift pump driver circuit open.Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONICCONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)Yes >> Go To 66. FUEL LIFT PUMP RELAY DRIVER CIRCUIT SHORTED TO EXTERNAL VOLTAGEMeasure the voltage between battery negative and the relay driver circuit in the PDC.Is the voltage greater than 1 volt?Yes >> Repair the Fuel lift pump Relay driver circuit shorted to voltage.Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONICCONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)No >> Go To 7DR/DH ENGINE - ELECTRICAL DIAGNOSTICS - DIESEL 9 - 1353P0628-LOW VOLTAGE DETECTED AT THE FUEL LIFT PUMP (CONTINUED)7. FUEL LIFT PUMP RELAY DRIVER CIRCUIT SHORTED TO OTHER CIRCUITSMeasure the resistance between the lift pump relay driver circuit in theECM connector and all other circuits in the ECM connectors.Is the resistance less than 10 Ohms?Yes >> Repair the Fuel lift pump Relay driver circuit shorted toanother circuit.Perform POWERTRAIN VERIFICATION TEST VER - 1(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROLMODULES/ENGINE CONTROL MODULE - DIAGNOSISAND TESTING)No >> Go To 88. ECMReconnect the ECM connectors.Turn the ignition on, engine off.Connect one end of an incandescent test light to battery negative.Connect the other end of the test light to the relay driver pin in the PDC.Using the scan tool, actuate the lift pump.Does the test light illuminate brightly?Yes >> Repair complete.Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONICCONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)No >> Replace the ECM.Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONICCONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)

[derez]

thanks im going to have to check my truck again and see if this is what i have going on.

[nilohamsi]

I heard about the same problem through one of my friends. The sounds will appear like the factory lift pump on the back of the filter housing finally failed. Without it the truck will not run at all unlike the previous 24 valve this truck will not run without it I have seen this often . It's covered under 100,000 mile warranty. Have installed a few the fix to remove the old one from the engine compartment and relocate the new one to the fuel tank like make sure that they retroit it to the in tank fuel supply pump also does not cost extra and should not have to ask for it but it should be automatic for them.

dodge ecu

Jeep pcm

[flagmanruss]

If this is the same as my 01, easy check is the battery connections. Power is off one side, ground off the other.