Had to do some hunting to determine the “normal” fuel pressure. It should be around 50-55psi. I know you noted the FPS was replaced, but what does it read with a computer hooked up?

See:
Fuel section of attached technical document
and

https://www.swedespeed.com/threads/info-on-2-4i-fuel-pressure-sensor-replacement-and-cel-clearing.201627/post-2546818

 

Thanks for the information. Going to have to try to get it to someone who can put it on a computer and see what's going on, as that's beyond our at home set up unfortunately.

 

VIDA will read relative fuel pressure 380 kPa, 55 psi, fuel gauge will show 480 kPa, 69psi.
See Hint below for relative and absolute difference.
Fuel pump duty cycle is 50% +/- 10%. You need VIDA or a better OBD reader to see duty cycle.
PEM varies fuel pump ground side = Duty cycle. Electronic on/off switch in the PEM controls fuel pump speed relating to fuel pressure. As the fuel pump wears out, the duty cycle will be increased to maintain fuel pressure.
I have the blue tooth obd reader from HF. It will read all of the computers on the car.
It displayed fuel pressure on my 15 XC60 but not fuel pump duty cycle.
This one does not have a monthly or yearly fee to use.
It does have internet search to help diagnose a code.
Do a SweedeSpeed search. I think someone cut a hole under the seat area to access the fuel pump.
If dropping the tank try to run it out of gas or very low on gas.
Go here to get a copy of VIDA and wiring diagrams 2005-2014.
Volvo Diagnostics – Virtual Machines, Installers and More

Fuel pump duty cycle.
Fuel pump control module, control signal - PWM signal pulse ratio 50% (+/-10%) engine at operating temperature PWM signal transmitted by the engine control module (ECM) to the fuel pump control module. The pulse ratio varies with the requested fuel pressure.



Overview
The fuel pressure sensor is combined and consisted of both the fuel pressure sensor and the fuel temperature sensor. The sensor detects the fuel pressure (the absolute pressure) and the temperature of the fuel in the fuel rail.
The fuel pressure sensor is on the right-hand end of the fuel rail.


Fuel pressure sensor
The pressure sensor is a piezo resistive type resistor, the resistance of which changes with the pressure. Depending on the pressure in the fuel rail, an analog signal of 0-5 V is transmitted. Low pressure results in low voltage, high pressure in high voltage.
The engine control module (ECM) then uses this signal to adjust the pressure in the fuel rail using the fuel pump control module. See also: Function:Fuel pressure regulation
The pressure sensor is supplied with 5 V and grounded in the engine control module (ECM). The pressure sensor transmits a signal indicating the fuel pressure to the engine control module (ECM) on a separate cable.
The engine control module (ECM) can diagnose the fuel pressure sensor. Its signals (pressure and temperature) can be read using VIDA.

Note! The absolute pressure is displayed when using VIDA parameter readout to read off the fuel pressure. If there is no pressure at the fuel rail, the atmospheric pressure will be displayed.
Hint:
The relative pressure (absolute pressure minus atmospheric pressure) is displayed when reading off the fuel pressure via a manometer connected to the fuel rail.

Fuel temperature sensor
The temperature sensor is an NTC sensor. The sensor is supplied with voltage (signal) from and grounded in the engine control module (ECM).
The resistance in the sensor changes according to the temperature of the fuel. This provides the engine control module (ECM) with a signal of between 0-5 V. Low temperature results in high voltage (high resistance). High temperature results in low voltage (low resistance).
The engine control module (ECM) uses the signal to calculate the density of the fuel.





Control
The engine control module (ECM) attempts to maintain a fuel pressure of 480 kPa (absolute pressure). A pulse width modulation (PWM) signal from the engine control module (ECM) to the fuel pump (FP) control module requests an increase or decrease in pressure. The fuel pump control module then operates the fuel pump unit to obtain the desired pressure using a pulse width modulation voltage on the ground lead. The fuel pump (FP) can be controlled steplessly by changing the pulse width modulation (PWM) signal. Only that pressure which is required at that specific time will then be released to the fuel rail/injectors. The value of the pulse width modulation (PWM) signal is a measurement of the operational load of the fuel pump (FP) (% duty, 100% = maximum pressure).
The engine control module (ECM) continuously monitors the fuel pressure using the signal from the fuel pressure sensor. This allows the desired fuel pressure to be achieved. If necessary, the signal to the fuel pump control module can be changed so that it corresponds to that required to achieve the requested fuel pressure.

 

Thank you for all the information!
I took my car to my nephew's place because he has a code reader that does live data. (This was before your comment with the additional information.)
After looking at things, we were finally able to find that the FPS I got was for the wrong engine code. We tracked down a new one and I was finally able to change it this morning.
I cleared the codes and put about 10 miles on the car and so far so good. Hopefully this solves the problem and I don't have to deal with replacing a pump.🤞