P0628 with functioning FASS fuel pump

[azrammedic]

Hi all new to the forum. Bought my truck a few years ago and even though I’ve cussed it out a few times during the learning curve I love it. I bought the truck already done up but now it’s giving me fits. The PO had the FASS red fuel pump installed. It’s functioning but the computer keeps throwing a P0628 and stumbling. The FASS pump was wired separately with power coming directly from the fuse box. The truck stumbles randomly and after inspecting the wiring I didn’t find any loose wires or exposed wiring. Anyone have experience with this?

 

[Fast69Mopar]

Hi all new to the forum. Bought my truck a few years ago and even though I’ve cussed it out a few times during the learning curve I love it. I bought the truck already done up but now it’s giving me fits. The PO had the FASS red fuel pump installed. It’s functioning but the computer keeps throwing a P0628 and stumbling. The FASS pump was wired separately with power coming directly from the fuse box. The truck stumbles randomly and after inspecting the wiring I didn’t find any loose wires or exposed wiring. Anyone have experience with this?

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I have dealt with this specific issue a few times. The biggest problem I have found is how the FASS Pump has been wired. You said the pump is wired to receive it's B+ power directly from the TIPM?

If you look at the set condition for this DTC it may make some sense.

DTC : P0628
Low Voltage Detected at the Fuel Lift Pump

Set Condition:

The commanded signal to the fuel lift pump circuit in the TIPM does not match the feedback signal from the Fuel Lift Pump Control circuit.

If the TIPM is not turning the lift pump on then it cannot provide the feedback signal that is needed.

Take a good look at how the pump is wired. See if you can determine what is providing switched ignition power to the pump.

Is the TIPM Fuel Pump Control Output circuit turning the pump on or is a basic switched ignition source turning the pump on?