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CEM Wiring/Repair Information

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Old Jul 4th, 2018, 22:43   #341
baldmosher
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Yep, I've still got 2 spare if anyone needs one.
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Old Aug 20th, 2018, 21:14   #342
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Quote:
Originally Posted by pierremcalpine View Post
That's a clever idea with little to no downside (except some time spent getting to the CEM, no biggy). Just out of curiosity, why WD40?
Great information in this thread, thank you all!

I had the same issue, no left hand low beam headlights on my recently acquired 03 S40. Replaced new bulb and new fuse and tried this "drill a hole + wd40 quick fix" but no luck. Also tried CRC O2 sensor cleaners and still no light. I guess I have no choice but to solder in new relays?
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Old Aug 20th, 2018, 21:52   #343
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Quote:
Originally Posted by WORLDCOM11 View Post
Great information in this thread, thank you all!

I had the same issue, no left hand low beam headlights on my recently acquired 03 S40. Replaced new bulb and new fuse and tried this "drill a hole + wd40 quick fix" but no luck. Also tried CRC O2 sensor cleaners and still no light. I guess I have no choice but to solder in new relays?
The WD40 trick may work if the internal contacts are just sticking a bit and the relay is in the early stages of failing. When the relay gets worse and worse, some of the internal contacts get slightly burnt and there will be no current flow, no matter what you try. I have refurbished over a 100 CEMs until now and I have taken all the old relays apart to check where the damage is and what was causing them to stop working. Anyway, new relays are cheap as chips and they are way much more better built than the cheapy original ones
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Old Oct 13th, 2018, 16:01   #344
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hi just to say thank you, what a fantastic fix. two relays from rs 20 mins start to finish getting old ones out a pain no special tools needed fantastic
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Old Oct 18th, 2018, 21:38   #345
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Originally Posted by Russell_S View Post
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
Does anyone know what the other 2 relays not marked up on the left hand side of the module control

Last edited by rudi dudi; Oct 18th, 2018 at 21:39. Reason: Typo
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Old Oct 19th, 2018, 01:32   #346
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1 Rear window wiper (P1CN012W1)
2 Windshield wiper (P1CN012W1)
3 Main Beams (NH010/01AY)
4 Left dipped beam (P1CN012W1)
5 Right dipped beam (P1CN012W1)
6 Parking light (P3CN012W1)
7 Rear and side marker lights (P3CN012W1)
8 Front fog lamp (56ND12-W1)
9 Rear fog lamp (P3CN012W1)
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File Type: jpg 7Vtv8v.jpg (92.0 KB, 126 views)
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Old Jan 14th, 2019, 08:53   #347
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I would love to be able to download Pdf's on CEM headlight and front beam relays but am unable to do so any suggestions. when I click the pdf's I just get a blank page and nothing else.
Thanks

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Old Jan 17th, 2019, 11:49   #348
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Originally Posted by teotodorov View Post
I would love to be able to download Pdf's on CEM headlight and front beam relays but am unable to do so any suggestions. when I click the pdf's I just get a blank page and nothing else.
Thanks

Teodor Todorov
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same here!
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Old Feb 8th, 2019, 22:56   #349
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Originally Posted by HannuKoo View Post
same here!
Guys seriously, post is great but pdfs are undownloadable... Please upload to a reliable server
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Old Feb 11th, 2019, 19:59   #350
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Question Fog Light Hell

I appreciate the thread and I'm hoping that I could just get some questions confirmed or clarified. I have a 2002 s40 that did not come with factory fog lights. After purchasing OEM fog lights and a OEM headlight/fog light switch, I later found out that the CEM needs to be programmed to enable the fog lights. I have read through the thread fully and from what I can see, I can buy a CEM that already has these enabled OR I can have them enabled in my CEM for a hefty price from the dealership. Correct? If I do purchase a CEM that is already enabled, are the part numbers the same over here in the US?

Is it possible to just bypass the CEM all together with my own relay and have it wired to the OEM fog light switch? I'm trying to make it look as factory as possible and avoiding an ugly rocker switch mounted under the dash.
I appreciate any help. Thank you!
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