V40: - 2003 V40 CEM Programming?

Fabi05 · Mar 21st, 2024, 22:41

Hi all,

I've read loads on this forum and used it for guidance a lot without being registered so thanks all - but I am having a bit of difficulty with something hence my first post.

I have a 2003 1.8 V40, I believe this would be a gen 1, phase 2 V40 as I have struggled to find a definitive answer to distinguish them.

I've had issues with the headlights for the past few weeks where they initially both became dimmed, then one went out, and finally both went out, before both came back on again (still dimmed) and now one is out again.

I've done a load of reading and I believe the issue lies with the CEM but this is what I am stuck on now. I've heard people say that replacing the CEM on my vehicle (2003/gen 1?) can just be done with the same part replacement and no reprogramming - can anyone confirm if this is the case?

I've also heard others say It HAS to be reprogrammed as it stores key information like VIN, Mileage, remote key/immobiliser informations etc.

I'd love any advice and guidance on this, thanks!

nokinnikon · Mar 22nd, 2024, 18:20

I've had this problem with my 2003 1.8 S40 (B4184S2)
The headlights going out and coming back on (usually damp and cold weather) turned out it was the relays in the cem. Found a couple of them online for a few quid, desolder them to get em out then resolder new ones back in.
With regards to swapping out cem for another just make sure your one has or has not the rear wiper version, why..?
Many have purchased the S40 saloon cem for a V40 estate version only to find that the S40 saloon cem isn't set up for a rear wiper, no re-flash needed. If you are good with a soldering iron then you are good to go. There are some photos on this site someplace to guide you. Hope this is of any relevance.

Here is the tread that you need

https://www.volvoforums.org.uk/showthread.php?t=67584

Fabi05 · Mar 23rd, 2024, 23:21

Hi, thanks for your reply. I've noticed it being mentioned in other forums too that the rear wiper , like you said and other features of the car such as the CC (which I never even noticed the car had until today) and Front fog lights would also need to be programmed if the donor CEM didn't come from a vehicle with these, I'll likely go down the route of buying a donor CEM. Do you reckon its worth trying to plug it in first and if anything doesn't work then sending it off to clone my current one? Not sure if that would mess anything up if I used it before having it cloned as I'm not familiar with the inners of how the CEM really works.

nokinnikon · Mar 24th, 2024, 16:15

Hi, you are welcome.

It's highly advisable to get a donor. Match numbers to numbers, plug in and try, cause if I'm right in remembering the re-flash/re-conditioning of one from a dedicated engineer will cost lots of money, here in the UK.
Caveat emptor regarding donor. Donor ones will/MAY have the same issues, as they are a known faulty item of our models of car.

Mar 21st, 2024, 22:41	#1
Fabi05 New Member Last Online: Yesterday 19:18 Join Date: Mar 2024 Location: Farnham	2003 V40 CEM Programming? Hi all, I've read loads on this forum and used it for guidance a lot without being registered so thanks all - but I am having a bit of difficulty with something hence my first post. I have a 2003 1.8 V40, I believe this would be a gen 1, phase 2 V40 as I have struggled to find a definitive answer to distinguish them. I've had issues with the headlights for the past few weeks where they initially both became dimmed, then one went out, and finally both went out, before both came back on again (still dimmed) and now one is out again. I've done a load of reading and I believe the issue lies with the CEM but this is what I am stuck on now. I've heard people say that replacing the CEM on my vehicle (2003/gen 1?) can just be done with the same part replacement and no reprogramming - can anyone confirm if this is the case? I've also heard others say It HAS to be reprogrammed as it stores key information like VIN, Mileage, remote key/immobiliser informations etc. I'd love any advice and guidance on this, thanks! Last edited by Fabi05; Mar 21st, 2024 at 23:03.

Mar 22nd, 2024, 18:20	#2
nokinnikon To Roll (Latin for Volvo) Last Online: Apr 26th, 2024 00:42 Join Date: Apr 2017 Location: Rhyl-North Wales	I've had this problem with my 2003 1.8 S40 (B4184S2) The headlights going out and coming back on (usually damp and cold weather) turned out it was the relays in the cem. Found a couple of them online for a few quid, desolder them to get em out then resolder new ones back in. With regards to swapping out cem for another just make sure your one has or has not the rear wiper version, why..? Many have purchased the S40 saloon cem for a V40 estate version only to find that the S40 saloon cem isn't set up for a rear wiper, no re-flash needed. If you are good with a soldering iron then you are good to go. There are some photos on this site someplace to guide you. Hope this is of any relevance. Here is the tread that you need https://www.volvoforums.org.uk/showthread.php?t=67584 Last edited by nokinnikon; Mar 22nd, 2024 at 18:30.

Mar 23rd, 2024, 23:21	#3
Fabi05 New Member Last Online: Yesterday 19:18 Join Date: Mar 2024 Location: Farnham	Hi, thanks for your reply. I've noticed it being mentioned in other forums too that the rear wiper , like you said and other features of the car such as the CC (which I never even noticed the car had until today) and Front fog lights would also need to be programmed if the donor CEM didn't come from a vehicle with these, I'll likely go down the route of buying a donor CEM. Do you reckon its worth trying to plug it in first and if anything doesn't work then sending it off to clone my current one? Not sure if that would mess anything up if I used it before having it cloned as I'm not familiar with the inners of how the CEM really works.

Mar 24th, 2024, 16:15	#4
nokinnikon To Roll (Latin for Volvo) Last Online: Apr 26th, 2024 00:42 Join Date: Apr 2017 Location: Rhyl-North Wales	Hi, you are welcome. It's highly advisable to get a donor. Match numbers to numbers, plug in and try, cause if I'm right in remembering the re-flash/re-conditioning of one from a dedicated engineer will cost lots of money, here in the UK. Caveat emptor regarding donor. Donor ones will/MAY have the same issues, as they are a known faulty item of our models of car.

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