I've read a lot of threads re: DTC P0628. Although the definition for the code is "P0628 fuel pump relay circuit low, or fuel lift pump control circuit low", it seems the remedy for this code for an "early 2004 CTD (where the lift pump is on the backside of the fuel filter)" is replace the lift pump since it is well known that it will eventually fail. Some replace it with the same or in-tank or install an AirDog or FASS (I'll decide later).

I can start the truck up just fine and its responsive to the petal. Obviously, it could just be the beginning of a problem and no sure how many miles can be driven before something fails.

First Q, can old batteries (i.e. you notice your headlights are dimmer / not a bright as before) with a lower voltage point cause these other more sensitive voltage components to trigger the P0628?

Second Q, how do I know which component is throwing the P0628? Can I do a specific test for each item?

 

if your under a 100k then its a warranty item since it is considered part of the motor. the weak battery mite have sent that code . i know when mine went on the 03 it went quick and didnt give any warning. a fuel pressure gauge will tell you the most info on the pumps condion 10 to 12 idle no less then 8 at wot

 

Did you check the fuse for the fuel pump yet? I have that code constantly because I pulled that fuse out (not using stock setup)...

 

Trik396,
I apologize, but I don't know where that specific fuse is located. I'll be glad to check it, if you could please tell me where to find it.

Rich,
Thanks for the info, but I don't have a fuel pressure gauge.

 

no problem... the fuse panel is located on the drivers side engine compartment directly in front of the battery. Unscrew the top and flip it over and it'll have a diagram as to where the fuel pump fuse is located below.

 

Normally, the P0628 is the death sign for the stock lift pump and like Rich said, it usually goes fast and leaves you stranded. Mine died getting on the interstate. If the truck is less than five years old and the mileage is under 100k the Cummins emission warranty will pick up the tab for the in tank replacement.

 

Mine threw that code on a Wednesday. On Saturday morning, my lift pump was dead and I was on the side of the road. I would be checking into a replacement lift pump ASAP, whether it be a stock replacement or an AirDog/FASS.

 

trik396, actually, I do NOT see a fuse in that box specifically for the fuel pump. I read the label and the closest thing that even states "fuel ...." are '12. 40A Fuel Heater, and 70. Fuel Heater Relay'. Maybe I do not know the letter abbreviations that are used, but I don't see a "fuel pump" label.

Could it be "23. 15A PCM, SKIM, OMTC" ? If so, then this fuse looks good.

I know its just a matter of time when the lift pump needs to be changed. but when I start it, I still hear the "fuel primer" noise (is this the lift pump noise?) going on (the 'wait to start' light). When the noise is gone (light goes off), I can start the truck with no problems.