based on what i’ve seen so far, it seems like the new version of the CEM (2014+) is made in such a way to avoid interfering/overlapping with the new options that can be added (because if you were to install the new CEM to a 2014+ car, no wiring should be required, and if you install it in a 2012, the newer CEM should still adapt to the car). i think engineering did that to avoid manufacturing several different Part numbers of the CEM (so basically, they would simply have only 1 newer CEM that can fit all xc70s, so a 2016 should fit a 2012 etc., BUT, a 2012 would not work on a 2016, so it’s only retro-compatible), but this is only a theory, based on my experience in engineering (aerospace, and trains, no cars unfortunately), it was definitely considered during the lifecycle design, to save cost, and storage space, not to mention the possible errors that can result from different part numbers for the “same” part.
i have checked several systems as a spot-check. the systems are the following:
- DRL: 2014+ and 2012 has different pins in the cem, so if you want to add DRL to a 2012 with new CEM, you will simply move the pins and do the wiring that is outlined above by @Juxols
- Rear folding headrest: the relay was integrated into the CEM on 2014+… strangely, it still worked on the 2012 using the external relay (if you look at the wiring diagram from a 2012, you will see the relay is external to the CEM, but for 2014+, the Relay is integrated within the CEM). this becomes a problem when you try to add the heated steering option (i.e. if you try to add that option in P3Tool), because heated steering wheel uses (What i think is) the same relay that was used for the rear folding headrests. so if you add the heated steering option in P3tool, you will automatically loose the rear folding headrest option until you wire it to the new CEM set up (the wiring is slightly different, it’s not difficult but still needs to be done to have both options)
- heated steering wheel option, the pins were empty (2012 didn’t have wires running to CEM pins that would interfere with the Heated steering wheel, so, relatively speaking, it was simple to add the pins to the CEM, but then you would have to rewire the relay that was used for the rear folding headrest to have it work as a heated steering wheel relay, that’s where i am right now, so i’m not 100% sure yet but i plan to do the heated steering retrofit over the next month or so)
i doubt that you will have issues with wiring (you will have to add fuses, and possibly some pins to the CEM for it to work properly)
programming is a whole other world, i have no idea how to approach it (how to program the CEM to match the car).
have you tried to install the newer CEM ?? and did you try to find the PIN using p3tool ?, i’m curious to know if it would come to life or not.
the CEM replacement bill that was supplied to me by the previous owner when i bought the car (mine is a 2012 XC70 T6 AWD) the breakdown was the following (bill is from a volvo dealership in the greater Montreal Region) :
- price of the new CEM
- 1.5 hr for wiring (maybe they just added some fuses, i didn’t see any rewiring, i accessed the CEM area and inspected it)
- 1 hr programming (not sure what that is, if i was to guess how to do it for people with P3Tool, i would read the old CEM, and store the settings, and then load them to the new CEM once i find the Pin of the new CEM)