S40 V40: CEM Wiring/Repair Information

[Muckeroja]

Hello just wonder the year of your car mate? thank you Paul

[sebaveh]

Well, it happen to one of our fellow volvo owner, who happens to know about electronics too. He soldered new relay in place and it worked. Later, he went to analyse the old relay part. He took it apart. Guess what he found - inside was another, smaller relay, soldered to pins of outer shell. How amazing is that ?!?!

[jordanfc]

Hey, Russel,
thanks for the critical info. even with my background of 30 years in electrical, instrumentation, and electronics, it was really difficult to troubleshoot a system whose engineers are information anal. i hope this doesn't break forum rules re language. i am new to forums. I have replaced engine and trans on my daughters 2000 s40, and have been appalled at the info access difficulties.

Thanks again
ps, re protocols, are the couple of capital letters I put in for emphasis considered bad form? also, is there a way to contribute $$ to forum support? It of course is much cheaper than Vadis subscription, or buying even more bogus Vadis copies! lol :-)

[jordanfc]

Originally Posted by Russell_S

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

Hi again Russel,
would be glad to pay for info, I have scoured the fujitsu database with no replacement relays compatible. no prob if just a relay base, but modifying the volvo cem prob not good idea. have you found replacement from any source?

[gatos]

Originally Posted by jordanfc

Hi again Russel,
would be glad to pay for info, I have scoured the fujitsu database with no replacement relays compatible. no prob if just a relay base, but modifying the volvo cem prob not good idea. have you found replacement from any source?

The idea of forums is generally to share knowledge for free. Payment would only be considered in cases where actual car parts are sold or sometimes when someone helps someone else to repair something (in most cases it's free too). The best way to pay back here is to offer your brains and ideas here so everyone else can benefit.....

[Kim4800]

Hey

Does anyone have the schematic for the cem? or knows what component there is on place DA13 and DA12? Mine has fallen off.... and I have to replace the components..

Kim

[sebaveh]

My wild guess - it might be a double diode with common anode? Do you still have it lying inside housing?

[Kim4800]

Yes only the one. A little black thing in a SOD323 case... And I think that there is printet B3 on it.. I think it is the same as DA15. But I need more to ordre it from a anyone

[Kim4800]

A BZX399C2V2 from Philips ?

[Commander]

Hi All, I am a very new member of the forum and would like to thank you all especially Gatos and jordanfc for all the info on this subject, spent two days reading up and printing off the wiring diagram started working on the car yesterday 27/02/15, at 10 am, soldered in two relays, all fixed by 16.30.
I have detailed the wiring diagram for high and low beams with the colour code but being a new member don't know how to put it on the site, To save time I also ran a wire from the Red lead connecting to the bulb (Disconnected from the bulb) outside the vehicle to the Drivers Footwell of the car and connected that to one of the probes on my multi meter and placed the other to the corresponding coloured wire to each of the headlight wires, that gave me a beep on my meter which told me that there was no break in the wire to that Headlight, also the same to the other side.
I also checked for voltage input to the CEM by removing the centre connecter of the CEM tracing the necessary wire (Yellow / Red and Yellow White) which confirmed that I had voltage into the CEM, that in turn confirmed all of your theory, Once again thanks to all, you save me a fortune