Volvo Owners Club Forum - S40 V40: - CEM Wiring/Repair Information

Volvo Owners Club Forum (https://www.volvoforums.org.uk/index.php)

- S40 / V40 '96-'04 General (https://www.volvoforums.org.uk/forumdisplay.php?f=17)

- - S40 V40: CEM Wiring/Repair Information (https://www.volvoforums.org.uk/showthread.php?t=67584)

Quote:

Originally Posted by Clan (Post 860254)

yes , just read your owner's handbook :-)

I have and in a P1 there is no option to do this ;/

Quote:

Originally Posted by Dog_Book (Post 860895)

I have and in a P1 there is no option to do this ;/

Sorry , you cant on the early one without cutting wires , after 2000 its simple and in the handbook ..

This information has been really useful! I have a V40 2.0T yr 2000 and in the shop they just said one of the two pairs of rear position lights (sorry about my Spanglish!) is not working. They claim this is due to the CEM, and of course offer me a nice replacement for 522 Euros! Do you know if there is also a relay in this CEM that controls those rear lights (there is one pair of lights on the trunk door and another pair on the main body of the car). Thanks!

Yes, inside CEM are two (2) relays for position lights.

-One is for inner (on trunk door) and for licence plate illumination.
-One for outer (on car body) and for front position lights (inside headlamp).

But first, check all the fuses, and a cable between trunk door and body. Due to a trunk door open and close, this cable can often break.

which the value of R47, R49, R11 and R122?

You are my new hero! Thanks for info hard to get from you kn

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 :-)

Quote:

Originally Posted by Russell_S (Post 470421)

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:
http://i93.photobucket.com/albums/l7...EMLocation.jpg

Next we have a picture of the CEM circuit board itself highlighting the headlight relays:
http://i93.photobucket.com/albums/l7...MPCBRelays.jpg

and now a picture of the CEM connectors and their pin numbering to go with the attached wiring diagram:
http://i93.photobucket.com/albums/l7...Connectors.jpg

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?

Quote:

Originally Posted by jordanfc (Post 931885)

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.....

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

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