S40 V40: CEM Wiring/Repair Information

[jimba]

I noticed on Russell_s original post, the wiring diagram shows the fog wiring as well. My V40 does not have the fogs, can I simply unsolder the relay for the fogs and place it in the faulty dip's place leaving the fog relay location blank? If so what of the relay numbers is the fog relay? (There are 6 identical relays on my board. Russell_s photo shows 4, an obvious difference in year or country) I'm assuming RLY1 or RLY2.
Thanks for any help you can toss my way.

[StephV40]

Hi,
Just want to thanks for this great thread! My right headlight didn't worked for a couple of months now and the fog light (and switch) I installed this summer, I coudn't managed to have them work... Visited 2 dealers and no answer on solution... (I have a V40 2002)
After reading this, I got a used CEM from a V40 2004 with fog, just swap with mine and headlight and fog turn on!!!
I'm a happy man!
Many thanks

[LizzieT]

Would you by any chance have a CEM for sale for 03 V40? No dipped headlamps but full beams work OK.

Originally Posted by 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.

[gatos]

Originally Posted by LizzieT

Would you by any chance have a CEM for sale for 03 V40? No dipped headlamps but full beams work OK.

Can you check the part number on it and let me know so I can check the ones I have? It should be 8 digits long and starting with 306 or 308. Are you sure it is your CEM that is at fault?

[LizzieT]

Pretty sure it's the CEM, local auto-electrician diagnosed problem back to the CEM. Same thing happened a couple of years ago, no dipped headlights and volvo quoted €500+ for the part. Eventually got one in a breakers yard although it was on an S40 as not so many V40s sold over here. Although Volvo parts claimed that it was an unusual fault when I rang around beakers yard lots of the CEMs were missing! Part no. I have is 30621305 which is the one from the S40, unfortunately I dumped the original. By the way, great forum.

[gatos]

As far as I am aware of, the part numbers don't differ between the S40 and the V40. The only difference on the V40 is the presense of the rear wiper which the S40 does not have. The only difference I have found out todate between the different part numbers of CEMs is the operation of the high beam. If a different CEM is used, then the high beams will not stay on when you pull and release the indicator stalk. There seems to be a link between stalks and CEMs. I definitely have a 30621305 so if yours was working fine all this time then my one should not be a problem.I will program the rear wiper and test all the functions of the CEM on my car to make sure it is fine. I will PM you my email so you can contact me.

[LizzieT]

Got the CEM and my headlamps now work perfectly. Thanks a million.

[gatos]

Originally Posted by LizzieT

Got the CEM and my headlamps now work perfectly. Thanks a million.

Thanks for letting me know. Hope this one lasts you for some time. Also, if you decide in the future to add fog lights, they will just be plug and play.

[zeverken]

Hello people! I am glad to have found this forum because you seem to be just the person who can maybe help me.

I've been driving around with a 2001 V40 for about a year now, with the rear wiper dead. The volvo dealer first thought the motor was broken, but after further diagnostics they blame the CEM (at a mind blowing cost of course).

From what I've read it looks like a CEM is fairly straightforward to replace with a second hand one. But I don't understand the 'programming' bit fully. Is the programming unique for every car? Is there a wrong CEM I can buy for a V40? You said you have some lying around. What would be your price?

thanks for reading!
best regards,
Zev

[gatos]

Hi Zev and welcome to the forum. When I use the term "programming, it may sound more complicated than it really is. What it really means, is that you can enable/disable a few options with the click of a mouse. See attachment.

The following components and functions can be activated:

The following can be programmed:

• Automatic low beam
• Twin headlamps
• Front fog lamps.
• Tailgate wiper
• Tailgate wiper when reversing.

There are a few different CEMs out there as they have changed something over the years. They are not car specific and you can easily swap them from one car to another. Here are the different models listed in VIDA:

Control unit [-2001, L.H.D (30859699)] 30896697
Electronics box [2002-, L.H.D (30621304)] 30638707
Control unit [-2001, R.H.D (30859700)] 30896698
Electronics box [CH 800000-026445, R.H.D] 30621305
Electronics box [CH 026446-, R.H.D] 30638708

Ideally you should try to replace the CEM with another one with the same part number. Saying that, I have tried a late 2000 CEM on a 2003 car and it worked fine. Only issue I am aware off, is that if you mismatch some CEMs, then the high beams are in "soft touch mode", meaning that when you click the indicator stalk backwards for the High beams, they don't stay on unless if you hold the stalk towards you.

Anyway, back to your problem. It is possible that the previous owner swapped a CEM taken from an S40, which has no rear wiper by default. In this case Volvo should be able to program it in less than 5 minutes. Or, it is possible that your CEM has developed a fault and it needs replacing.