I am having some major electrical issues on my S80. I recently purchased the vehicle, and all systems were functioning perfectly, up until about 12 hours after buying it.

Coming home from a trip, my lights (low beams and corner lens), cabin climate control, radio, windows, sun roof, passenger power seat, reverse lights, and most non-engine systems all suddenly stopped working. I had just adjusted the sunroof and we heard a click, then all listed systems failed. The sunroof was operational up until I stopped the car to diagnose. After attempting to diagnose the issues, we noticed that sun roof had now failed, and the gear shifter would not allow us to select a gear (would not move out of park.). We are able to select a gear, so long as the car is not actually started.

We have tested most fuses that we could find (I.e. Cabin fusebox, trunk fusebox, and engine bay relays/fuses.). All fuses are fine, which led us to the CEM for diagnosis. The shunt that causes many people grief looks fine, no charring or oxidation. In fact, all connections and wires seem to be intact and clean. Extremely clean compared to my 87 300zx which was forever plagued with electrical issues.

Highbeams, drivers seat, and interior cabin lighting (minus the dash accessories backlighting), and dashboard instruments all work, along with the parking lamps, so long as the headlamp selector switch is not switched to "headlamps on".

We are at a loss of what else to check, not to mention that information has been scarce. We have also tried the key reset, as well as the battery terminal reset, none of these have effected the symptoms listed. We were able to get one low beam light to shine when we removed the low beam relay from the cem, but only when I used the high beam stalk switch.

Any information or hints would be much appreciated. I bought this vehicle specifically because I was tired of working on my z, and now I am knee deep in a nightmare 1000x worse than any issue my z ever threw at me. The car is now undrivable, due to no lights or wipers nor being able to select a gear, so I am dead in the water.

 

You need to pull the codes. I'm guessing, but you may need a new alarm module which is located in the front right fender. It has failed and is causing your electrical issues.

 

I chased and traced the issue all day today with zero progress. In the morning I will be having a local volvo specialist (non-dealer) read the codes and suggest a plan of action.

However, your comment on the alarm module is very intriguing. Would the alarm module fault also cause the lowbeams not to work when selected yet allow the highbeams? What about the passenger seat not working and the drivers seat still working? I find this hard to fathom, honestly, and I am not doubting you, but I'd like an explanation of how you came to that conclusion. Forgive me, but I am formerly a Nissan guy, and the Swedish style of things is extremely confusing to me right now.