I can only tell you what it says in VIDA. I don't think the T8 diesel engine is in the 2015 version of VIDA, so that will be why the fault only comes up for the T14 engine.
If the fault returns when cleared, it's still present. From the description in VIDA, the cause has to either be the EGR pump or the wiring - an open circuit in the signal cable is specifically described, suggesting a break in the signal cable or connection interrupting the circuit if the fault is not with the pump itself. So the two options appear to be to check the wiring, connector pins etc. for continuity, hidden corrosion or breaks in the cables etc., and/or try another pump.
The DTCs are generated from voltage and resistance monitoring of the wiring connected to the part. Obviously if the pump is faulty, the wiring signals will be out of expected range, and the DTC will show. But it can also be triggered by a wiring fault (open or short circuit, high resistance due to corroded or poor connections etc.) that also affects the voltage or resistance in the circuits. As I say, the description in VIDA indicates a short circuit in the signal cable as the likely cause for this DTC if it is not a fault in the pump itself.
I'm afraid there's not much else I can suggest really, although with parts that are subject to fault monitoring, I have to admit that I usually go to a Volvo dealer or OEM supplier for the part, and avoid cheaper pattern parts. I've had experience with pattern parts that return incorrect values, either because they are generic or because the vehicle manufacturer has changed the specification for some reason. A Volvo dealer will know that by looking up the part against your VIN. Any in service modifications will be shown on his system, which is not always the case when ordering pattern parts. So I would at least check the correct current part number with Volvo and either obtain it from them or look for the correct part by part number and manufacturer, if you know who makes the OEM part.