The red tail lights on the tailgate hatch were out on my 2000 V40 (165K miles). The dealer diagnosed the problem as a bad CEM (P/N 30859699).

I bought a used replacement CEM on line, which fixed the tailgate lights, but then the rear wiper stopped working. (Returning my CEM fixed the wiper again). I exchanged the new "bad" CEM for another used unit and had the exact same experience - fixed tailgate lights, wiper no longer works.

All three modules are marked with VOLVO 30859699, CENTRAL ELECTRONIC MODULE LHD 3817900-150.

Are there differences between CEMs? Any ideas?

Thanks much!

 

when CEM swapped they may be coming out of a S40 (have no rear wiper and de-activated the rear wiper function). To fixed this issue have to hook up VIDA or VADIS (dealer specific diagnostic tool) and activate rear wiper option under vehicle communication tab that will most likely fix it.