S40 V40: CEM Wiring/Repair Information

[baldmosher]

Originally Posted by Commander

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

1. "Go Advanced"

2a. click the paperclip icon, a new popup/window will open
2b. click Choose File
2c. select your file (must be quite small so you might have to shrink it down in Paint first)
2d. click Upload
2e. check it's worked then close that popup/window

3. click Submit Reply

[Roman62]

Hi,
Is the CEM and ECU one and the same?

I was told by a local Volvo "expert" that the CEM is coded and can only be used on the same car. Is this true?

[gatos]

Originally Posted by Roman62

Hi,
Is the CEM and ECU one and the same?

I was told by a local Volvo "expert" that the CEM is coded and can only be used on the same car. Is this true?

No they are not the same. There seem to be a couple of different model numbers for the ECU on the S40. I have tried the ECU from a 2001 1.6 S40 on my 1.9D and everything was fine.

What exactly are you trying to do?

[960kg]

...if you can locate the relay in the CEM just replace it you will need a soldering iron!...B2 on the wiring diagram leads to it...all modern relays are available on the internet outlets somewhere you just have to do your own homework..

[960kg]

Originally Posted by 960kg

...if you can locate the relay in the CEM just replace it you will need a soldering iron!...B2 on the wiring diagram leads to it...all modern relays are available on the internet outlets somewhere you just have to do your own homework..

.....IGNORE answered wrong thread!!!!

[71impala]

Thanks to all of you who have posted on this site.

Had the same cem problem on my mate's s40.

Bought a relay at RS for a couple of quid, removed the old one from the pcb and soldered in the new one. Lights now all work as good as new and without the horrible expense.

I'm not great with a soldering iron but managed to do this ok by taking a bit of time and going at it gently. No-one should be put off from giving it a go.

Once again Thanks.

Pete.

[MidlandsV40]

Afternoon all - after Googling issues with headlights I was directed to this forum and joined.

I have a 2003 V40 estate. Last year the LH beam failed, after taking it a workshop I was told that allegedly the CEM maybe at fault and the quickest way to get both lights sorted was to run a feed from the working RH side light to the left. This worked fine until last week when both lights failed on a drive back in the dark, not a good situation.

I spoke to the garage and they said after checks on the car that the CEM was the likely culprit? I have flash and fog lights but no sidelights nor main beam. As some have already stated a replacement from Volvo would be £450 + VAT and then a further cost to get the unit coded to the car.

Can I just double check with you guys that are more knowledgeable than myself, is the problem the relays that are pictured on the first page of this thread? Also there is a link to a supplier. Am I right in thinking that I need to replace all 3 relays on the board , if so is this the fix for the headlight issue?

Also if this is the case and it gets done will the unit just be a case of being plugged back in without need of registering it?

A huge thanks in advance.

[Buzzvolvo]

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

Thanks for this detail on the CEM. Headlight relays for Fujitsu are now obsolete but Farnell were able to supply a replacement JSM-12-5 which is an exact fit rated at 15A cost £2 to £3 pounds (downside is Farnell have a minumum order of £20) excellent delivery.

A fairly easy procedure to replace provided you have a soldering iron and a solder sucker.

regards
Buzz

[stuhandy]

Hi there, My CEM has given up the ghost so I will be replacing it. If I use another CEM does it need registering to the car or is it plug and play? Regards Stu.

[gatos]

The CEM should fit on the car as it is with no need for programming. However, certain functions might need programming, ie fog light and rear wiper.

However, if the replacement CEM came from a car with fog lights on it, then you will not have to program it for fog lights. If you have a V40 and the replacement CEM comes from an S40, you will need to program the rear wipers to the CEM. However a V40 CEM will work on an S$) as is.

What car have you got? I have an S40 CEM and Siamblue has a V40 CEM, both with fog lights, so no programming will be needed.