LH low beam not working - 05 XC70 Topic is solved

Post by **scot850** » 23 Jul 2026, 19:48

Someone was given my name to see if I could help with an issue they are having. They have recently moved to Alberta and have to re-register the car in Alberta and need the lights to be working! He is hoping to come over Sunday for some help.

He has so far checked the fuses, even swapped the headlights (they are halogen) and nothing has worked.

Looking at the wiring diagrams (regulars know how much I love electrical work!!

) , it looks to me that the issue may be the CEM as a guess. I am not as familiar with the newer P2's and the likes, but can usually troubleshoot if I understand how the circuit works.

My thinking is it has to be something that is unique to the LH low beam.

1) I would think the headlight itself is ok, if swapping another in also did not work (they don't have ballasts if I recall as they are halogen).
2) I would suggest it is not the headlight switch as I would expect from the wiring diagram that it operates both headlights through the CEM and so they are not individually switched
3) The turn-signal/hi/lo beam switch looks like it operates the same way.
4) I am at this point assuming he has checked the bulb, but I will check again.

So the only thing I can think of is a relay. I think I read that there are separate relays for LH and RH on the CEM. Is this correct?
I have read that the CEM can cause this sort of issue. Can the relays be replaced easily, and if so, where do you get them?

The only other thing would be a wiring or connector issue between the CEM and the headlight unit connector.

I am not particularly proficient with Vida, but other than maybe a code, is there anything that it can do to help diagnose the issue?

Any help is appreciated!

Neil.

Vova585 · Post by **Vova585** » 23 Jul 2026, 22:16

I would start with the basics and try to cut this diagnosis short(unless the guy is a cool volvo dude and brought pizza and beer).
Based on my quick look at the diagram, I came to the same conclusion as you in terms of CEM supplying the power to the low beam.
We dont know if the owner tested correct wires and what equipment he was using.
If he was substituting the headlight for another and nothing happened- amazing, time to figure out what is missing(power or ground or both).
I would use a substitute load testing method with a good test bulb(H7 works amazingly for this). Verify your test light works and through T-pins(needles, proper needle type connectors from amazon etc) check the ground first( appears it is on A4 pin). So 1 wire at nice service 12v+ port and next to A4. No light- lets try to substitute the ground from chassy to A4. Bright light-amazing, 31/93 should be found and hopefully the problem is there.
If the ground checks great...Then lets check if we have power at A2. Can use A4 in this case as ground, but i prefer 1 probe in connector not to short anything(as usually we would verify test equipment and check for good ground via connecting service bulb between chassy/engine metal and 12v+ port. Bright light- possibly he broke the connector or pin tension is gone since someone was using multimeter leads to test prior to you.
If no "light"..then lets watch xemodex video "how to remove cen on P2" and get access to CEM in engine compartment. I would prefer to have a piercing probe here(cheap on amazon..like 12-15) and pierce the wire BL-W that goes to B7 of CEM. If no "light" even thede...well xemodex is doing magic..

Post by **vtl** » 24 Jul 2026, 07:01

I had to fix a melted/corroded connector on my 05.

New headlight would not help in such case.

Otherwise check voltage on the connector, then on the fuse. If fuse is not blown and has no voltage - need to replace the relay. It is unfortunately soldered to CEM.

Post by **vtl** » 24 Jul 2026, 07:04

Vova585 wrote: 23 Jul 2026, 22:16 If no "light" even thede...well xemodex is doing magic..

Soldering iron + hot air combo is under $100 on amazon. Unless bad water intrusion was found inside the CEM and it needs a more involved brain surgery than replacing a relay.

Post by **scot850** » 24 Jul 2026, 17:27

Thanks guys. I have a electrical test probe and even end-to-end test gear (never been used!!

). Thanks for all the suggestions and guidance, it is always really appreciated.

I will start at the beginning and work my way through. First thing is I will get a full list of what has actually been done to make sure no obvious mis-information is part of this process.

I worked in electronics manufacturing and have a higher end small tip soldering iron for rework on circuit boards. Hot air de-soldering would be a great help and may investigate this further. For the few board repairs I have ever needed to do it has so far not been necessary to buy one. One of my son's friends Dad works for an electronics repair shop so might just ask him to do it for a beer donation.

Hardest part will be finding the correct relay. I have found sources specifying what it is, but the manufacturer (Tyco) are not longer making it. There are suggestions for an alternate but not found a source for it yet.

Neil.

Vova585 · Post by **Vova585** » 24 Jul 2026, 21:28

Please pardon my lack of knowledge on this subject. I would just hypothesize that CEM might have lots of similar relays. So in case we have a person with high end soldering skill(which checks) he can possibly transplant a similar relay from donor CEM(which should not be a problem given ammount of cars produced) vs possibly just "retrofit" a common relay(once again sorry for my lack of knowledge, I compensate with my "magical thinking" and trust in wizards of electronic boards). That can be attached somewhere close to CEM(sorry analogy with Chrysler TIPM).

Post by **vtl** » 25 Jul 2026, 07:47

Yes, either transplant a donor, or find a similar function relay that plugs into socket and use a file or Dremel on its pins. This relay is nothing special, besides pins.

Post by **scot850** » 25 Jul 2026, 08:52

I agree, There are relays out there, but it is a lot of work to fit something that is an unknown. We will have to cross that bridge when we get there. A substitute from another board may be the way to go.

I'll update when I have more info.

Thanks guys.

Neil.

Post by **cn90** » 25 Jul 2026, 09:21

1+,

As mentioned, always work backwards...

1. Check the HL bulb first.

2. Then check the wiring, connectors (rodents chewing wires etc.) and trace it back to CEM.

3. Once you determine the relay (Tyco) to be problem, remove the CEM and desolder the Tyco relay and install a new relay.
Sometimes, it is NOT the relay but rather "dry solder joints": in this case, resolder it.

@vtl posted good info here...

https://www.swedespeed.com/threads/cem- ... 532/page-2

The relay is Tyco V23134-J52-X455.
The company is no longer with us, the replacement is TE V23134-J0052-X455.

PS: Circuit diagram for 2005-2009 S60 below...It is just dumb to solder a relay directly into a circuitboard.
Back in the good old days, the relay is separate and you simply unplug and reinstall a new relay.

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: HL-S60.jpg (49.44 KiB) Viewed 965 times

Post by **vtl** » 25 Jul 2026, 11:33

cn90 wrote: 25 Jul 2026, 09:21 It is just dumb to solder a relay directly into a circuitboard.
Back in the good old days, the relay is separate and you simply unplug and reinstall a new relay.

That means a $5 part DIY replacement job becomes a $1,600 new CEM + dealer's hourly rate to program it + taxes ~ $2,000. Or, as Volvo and others hope, becomes a new $50,000+ car purchase.