Hi, I've recently had a headlight problem which, at first, appeared to be the common CEM issue (see this thread
http://www.volvoforums.org.uk/showthread.php?t=67437) but finally turned out to be a break in the wiring loom. However, while fault finding the problem I found out a bit about the CEM which I thought others could find useful in faulfinding their own headlight related issues. I've taken a few pictures to help with this.
I have attached to this thread the Volvo wiring diagram for the CEM and headlights because the Haynes manual is worse than useless in this respect as it doesn't even show the CEM in their wiring diagrams.
I have also attached the data sheet for the Fujitsu relays that are used for the headlight switching in the CEM. I originally assumed that they would be solid state relays but in fact they are normal miniature PCB mounting mechanical relays so it they do fail then the data sheet could help find a replacement to repair the CEM.
Firstly, for those who don't know where the Central Electronics Module (CEM) is situated, here is a picture:
Next we have a picture of the CEM circuit board itself highlighting the headlight relays:
and now a picture of the CEM connectors and their pin numbering to go with the attached wiring diagram:
Hopefully others will find this information useful as the CEM does appear to be a weak component with respect to headlight switching.
Regards
Russell