From 372: CEM-3F90 Fuel pump relay. Open circuit or short circuit to ground. The following applies to vehicles with fuel pump module (PEM): Central electronic module (CEM) checks the voltage feed to the fuel pump module. The Central electronic module (CEM) activates the voltage supply to the fuel p...

Shockwave...found this crawling the web, unverified

Link

https://www.picoauto.com/support/topic14491.html

Waveforms if ECU and PEM to drive pump

https://www.picoauto.com/support/topic14491.html

Here's the thing, I forgot to mention that I wasn't actually having fuel pressure issues! My car ran great, it was just throwing the code at me. No stalling, no sputtering or loss of power like others describe. I've been monitoring the fuel pressure with my OBD2 reader and it was perfect even with t...

That’s a real gem of troubleshooting info. The clutch switch is integrated into the cruise, so that the engine doesn’t race when you declutch. Starting with clutch engaged is telling that the switch is dead, though. If you have a good code reader that can monitor fuel pressure you’ve done well. One ...

My car has about 100K miles and has been very reliable. A month ago, I suddenly had some hesitation at highway speeds when going straight and level. This first seemed like a auto transmission issue to me. After a few weeks, where there were some additional issues at lower speeds (always when the car...

Exactly on cue for time and miles when my 2005 V70 PEM did the same thing. Thanks for an informative post

Part numbers

8634953 30769225

Both codes have a faulty fuel pressure sensor (FPS) in common. FPS is on the end of the injector fuel rail and there are a couple "direct fit" alternatives to the pricier Volvo stamped Bosch part. Went looking for another post and see this one- http://volvospeed.com/vs_forum/topic/154942-2...

Checking the PEM off the car is very very difficult.

Your best bet is to find a good used PEM (ebay, junk yard, good known PEM from another car) and swap over.
If the swap fixes the issues, you know the answer.

PS: The corrosion is internal (on the circuit board) of the PEM.

Possible sources

• Leakage in the fuel lines
  Blocked fuel filter or other restrictions.
  Dirt, debris, or loose objects in the fuel tank.
  Damaged fuel pressure sensor
  Damaged fuel pump
  Damaged fuel pump control module.