Swap out ECU on a 2004 Volvo V70 2.4?

[oragex]

You have 2004 MY car. For this year there is typically problem - bad CEM. If you can hear some clicking sounds like relay from CEM area when problems come in, this means your CEM need replace.

It may indeed be a CEM water ingress issue, you may have a look at it see if there's water marks on the box - look up on Youtube
It can be repaired by Xemodex


There is also a computer called ECM, located in front of the power steering reservoir. Hopefully not faulty as this has to be replaced with a new unit$$$$$ from Volvo. This one can fail if it overheats, usually because the small cooling fan at the back of the box has failed.

[yagger]

Actually, CEM communicate with others modules use 2 CAN-buses High-speed bus and Low-speed bus.
ECM use High-speed bus. And if problem in ECM I can not explain this:

Also the windows and doors become inoperable.

because DDM and PDM use Low-speed bus.
There is problem in CEMs 2004 MY (Flash memory). Problem come in when this flash memory getting hot (or warm). Replace it can help, but you need remember, there is very unreliable pads on PCB, and any solder works, can broke your CEM. More info, need reprogram this stuff also, and I know many many cases about lost correct info from original CEM when somebody tried program it itself.

[yagger]

Also, water ingress issue typically for 2005 - ..... MY CEMs.