S40 V40: CEM Wiring/Repair Information

[gatos]

Originally Posted by youngmun

Hi, I have just replaced the CEM on my S40 with one from a V40 (same part number) and I am getting 'key error, try again' message. Tried battery reset, no luck. How can I resolve this, do I need to get the key or the CEM reprogrammed? I am thinking of putting the old one back on again but wonder if there are any other ideas out there, before I do this. Thanks.

As far as I am aware off, the CEM has nothing to do with the key. So not sure if there is a link or it was just a coincidence.
Can you provide a bit more info? Year of car, engine type and size?
What was the problem that made you change the CEM?
What was the part number of the old CEM and the replacement one?
Where exactly do you get the 'key error, try again' message?
Does the car start and drive?

[youngmun]

Hi Gatos,

Thanks for the response.

My car is an S40, 55 reg, 2.0 D. CEM part 30728906 which I had replaced with same part number CEM from a V50.

I have been getting problems with the doors failing to unlock, esp the front passenger door, inaccurate outside temperature (-40, or -----) and sometimes homecoming lights coming on without prompting. The problem seems worse when it rains! My indie advised few months ago when I had a major problem with doors not unlocking that it was likely the CEM and that they had also cleared a lot of fault codes which led them to strongly suspect it. They also did some work to prevent possible water ingress which they said may have affected it.

On replacing the CEM yesterday the car would not start at on turning the key, and it read 'key error, try again' in the display after a few minutes of inserting it.

Speaking to my indie and Volvo, they say the car has to have a software download to enable immobiliser and other security functions but will only work if the CEM is brand new, i.e. has not previously been programmed to a particular car's settings.

I have since put the old CEM back on the car and everything works fine like before (temperature reading -38 of course). I'm frustrated that it really looks like I have no other alternative but to buy a new CEM at eye watering prices to fix the problems above.

I also wonder if it might be the passenger door module rather than the CEM, given most other electrics work fine? When I give the side of the passenger door some firms knocks, sometimes this unlocks the doors!

[gatos]

I am afraid this section of the forum is for the earlier S40/V40 cars from 1996-2004. You will have more lack asking the same question in the right place http://www.volvoforums.org.uk/forumdisplay.php?f=58

The CEM function on your car involves a lot more parameters and has something to do with the keys/locking. See what people say in the right section of the forum and with a bit of luck a forum member with a Volvo DIE, local to you might be able to program it for free. See the map of users with DICE here: https://www.zeemaps.com/map?group=280351

http://www.volvoforums.org.uk/showthread.php?t=136759

Hope this helps

Also this is the list of things that can be programmed in the CEM for your car

[Clan]

Originally Posted by youngmun

Hi Gatos,

Thanks for the response.

My car is an S40, 55 reg, 2.0 D. CEM part 30728906 which I had replaced with same part number CEM from a V50.

I have been getting problems with the doors failing to unlock, esp the front passenger door, inaccurate outside temperature (-40, or -----) and sometimes homecoming lights coming on without prompting. The problem seems worse when it rains! My indie advised few months ago when I had a major problem with doors not unlocking that it was likely the CEM and that they had also cleared a lot of fault codes which led them to strongly suspect it. They also did some work to prevent possible water ingress which they said may have affected it.

On replacing the CEM yesterday the car would not start at on turning the key, and it read 'key error, try again' in the display after a few minutes of inserting it.

Speaking to my indie and Volvo, they say the car has to have a software download to enable immobiliser and other security functions but will only work if the CEM is brand new, i.e. has not previously been programmed to a particular car's settings.

I have since put the old CEM back on the car and everything works fine like before (temperature reading -38 of course). I'm frustrated that it really looks like I have no other alternative but to buy a new CEM at eye watering prices to fix the problems above.

I also wonder if it might be the passenger door module rather than the CEM, given most other electrics work fine? When I give the side of the passenger door some firms knocks, sometimes this unlocks the doors!

you are wasting lots of time and effort and money here , if you had taken it to a volvo dealer they would have told you it is MOST likely the door wiring connector , there was a recall for this and your car may be still covered for this . CEMs contain immobiliser details and are locked to the car they were built with If it is faulty it must be replaced with a new one ...

Was there any sign of wetness in the big green plug or CEM pins on the top right of the CEM ? That would be the wash pump pumping water up the loom ! unlikely but possible .. again a recall would have sorted this if the case .

[youngmun]

Thank you Gatos & Clan for the helpful information -esp.about what can be programmed for the CEM & advice about the door wiring connector, much appreciated. There was no sign of wetness, it was definitely dry.

My plan is to have another word with my local Volvo on Monday and see what they say alongside your suggestions. Hopefully I can get a speedy resolution if it's the door wiring connector- I did check it sometime last year and I am sure it was gold plated with no signs of corrosion but will see what Volvo say.

Thanks again.

[Clan]

Originally Posted by youngmun

Thank you Gatos & Clan for the helpful information -esp.about what can be programmed for the CEM & advice about the door wiring connector, much appreciated. There was no sign of wetness, it was definitely dry.

My plan is to have another word with my local Volvo on Monday and see what they say alongside your suggestions. Hopefully I can get a speedy resolution if it's the door wiring connector- I did check it sometime last year and I am sure it was gold plated with no signs of corrosion but will see what Volvo say.

Thanks again.

if it was gold then you would have already had the repair done . Just removing and refitting the plug should have a positive effect on the operation if it is playing up as it cleans the contacts .

[youngmun]

Hi,

Volvo confirmed yesterday that the recall work on the door wiring connector was indeed carried out. I will try your suggestion of removing & refitting it and see what happens.

Thanks!

[SteveV40]

I have just replaced the relay on my V40. Never done anything like it before, but it only took 45 minutes start to finish. Got the relay from RS in advance. I bought 3 for less than a tenner including postage. Many thanks to everyone who has posted on this as it has resolved a problem that has saved me having to find a replacement CEM. They all differ, and this was a much more straightforward solution than I imagined.
I thought I might add my notes for anyone wishing to try this.
The relay has 5 soldered points, and they are quite close together. Ideally you would heat all 5 at the same time to pull the relay free, but I only had a standard soldering iron. I started with the two end ones and heated them in turn one at a time, gently easing the relay a little at a time until the came free. I them went to the three at the other end, and followed a similar procedure, although it was less straightforward due to the close proximity of the 3 terminals. Gentle leverage with a small screwdriver underneath whilst heating each in turn eventually persuaded it clear. 4 of the 5 holes were partially obstructed by solder, so I wrapped some tape (for heat insulation) around a darning needle and then heated the solder wiggling the needle in as far as possible, and then wiggling it free as the solder cooled. repeating several times on each hole until they were clear. Then mated up the new relay, added some new solder to the terminals, being careful nor to spread it around, and back into the car. Absolutely thrilled when the headlamp came on.
Thanks to all, and hope this helps encourage someone else to try this. Best wishes.

[Matt86]

Originally Posted by SteveV40

I have just replaced the relay on my V40. Never done anything like it before, but it only took 45 minutes start to finish. Got the relay from RS in advance. I bought 3 for less than a tenner including postage. Many thanks to everyone who has posted on this as it has resolved a problem that has saved me having to find a replacement CEM. They all differ, and this was a much more straightforward solution than I imagined.
I thought I might add my notes for anyone wishing to try this.
The relay has 5 soldered points, and they are quite close together. Ideally you would heat all 5 at the same time to pull the relay free, but I only had a standard soldering iron. I started with the two end ones and heated them in turn one at a time, gently easing the relay a little at a time until the came free. I them went to the three at the other end, and followed a similar procedure, although it was less straightforward due to the close proximity of the 3 terminals. Gentle leverage with a small screwdriver underneath whilst heating each in turn eventually persuaded it clear. 4 of the 5 holes were partially obstructed by solder, so I wrapped some tape (for heat insulation) around a darning needle and then heated the solder wiggling the needle in as far as possible, and then wiggling it free as the solder cooled. repeating several times on each hole until they were clear. Then mated up the new relay, added some new solder to the terminals, being careful nor to spread it around, and back into the car. Absolutely thrilled when the headlamp came on.
Thanks to all, and hope this helps encourage someone else to try this. Best wishes.

A de-soldering pump tool makes this job easier as well.

[Clan]

If i had to do this i would run the wires from the solder pad outside the CEM and connect to a good old 40A relay . no more troubles then :-)