Volvo dash codes ISX engine

[Ronnie4447]

Got a couple of codes through Volvo dash diagnostics for my ISX MID 128 PID 94 FMI 4 and the other is MID 128 PID 94 FMI 1
Any idea what these are they are both inactive but when they are active truck runs rough
I replaced crank shaft sensor yesterday because tach wasn’t working all the time, fixed that problem but it’s doing this now. Done this one time before and it was fuel filters, changed them and it still doing it after changed but now it seems to be running fine could it been the filters and just took a little while to straighten out. HELP I’M LOSING MY MIND over this Volvo
Thanks in advance

[Chamberpains]

They are both fuel pressure codes. Yes it can take a little while for air bubbles to pass through when changing filters or when the fuel system and gets a lot of air in it.

When you turn your key on without starting the engine do you hear your lift pump buzzing nice and loud or Does it sound really choppy? If its really choppy it could be a faulty lift pump or it's sucking air.

[Ronnie4447]

yes I do hear the pump but it does sound choppy, like it is under load then not under load the pump was replaced when the engine was built 270000 miles ago