Check the multi pin connectors to the CEM and in the driver's footwell behind the carpet against the kick panel. Break and if necessary clean the terminals with an electrical contact cleaner. I'm not saying that's definitely your problem, but it's a known cause of multiple unrelated fault warnings and errors. There are several related threads on here, including a recent one that included a photo of the connector in the footwell.

 

Thanks.
Are you referring to the assembly shown in this video?

 

no, have a look at this post?

https://www.volvov40club.com/threads/2014-v40-d2-dash-warnings.39146/#post-319709

 

The link that Tony posted above shows the footwell connector. The CEM is behind the glovebox and those connectors should be checked also, but I wouldn't go to the lengths of removing the CEM, at least initially. You should be able to unplug the connectors from it without unmounting the module itself. It may be that just unplugging and reinserting the connectors will be enough to clean the contact pins, but if not sparing use of a contact cleaner won't hurt.

I would disconnect the main battery negative lead before unplugging any of the connectors, to be on the safe side

 

As @RS3100 told you, first disconnect the battery.
Open the right front door. Move the seat to far back to open as much as possible space there. Remove the sill with the inscription "Volvo" on it. It is on clips, just gently pull it up. Now you can turn the carpet back and will see so many connectors there below the right side of the glovebox. Some of them are surrounded by a white plastic "fence", which is easy to open. Turn the carpet as much as possible and near the floor will see other connectors, too. Just behind the glove box there is the CEM module(this one, with many fuses on it) with other connectors on it. Try to disconnect and reconnect all that connectors and maybe spray them with some contact cleaner.
But be careful, connectors with two orange thick "cables" are not cables, they are optical fibers and don't touch them, they are not an electrical wires. Also, they don't like bending and can break internally because they are made of glass. Don't spray them with anything.

 

Many thanks for your help; will give it a try one of these days.

 

Coming back on this. Turns out that my issue was due to my battery dying. No "Low Battery" warning appeared, but had it measured and it was almost dead. After replacing it with a new AGM battery, the issue has not appeared for the past 2 months.

 

I have the exact same problem, changed the battery, but the codes kept coming. This has bothered me for a few months now and I can’t find a fix. Can you please tell me what you did?!

 

@larskupen in my case the problem almost vanished after getting a new battery. It has appeared only twice in the last year. I went to an independent Volvo garage that told me it is known issue with the wiring connections; they pretty much wanted to keep the car for 2 weeks, strip off all the carpet and re-solder everything...not gonna happen. It's a pity that Volvo has not made a recall for this issue. You can probably follow the recommendations from other forum members and try to clean the connectors on the footwell and also tighten the 2 ground connectors (I believe one is in the hood by the battery and the other is behind the carpet in the driver's side - someone pls correct me if I am wrong).
Good luck!

 

I just changed the battery today. It ran good, and I tried to blast some music and then after a few minutes the codes popped up and I couldn’t start the car. Left it locked for a few minutes and I was able to start it again. I left the car running for about 40 minutes and no codes popped up. I think it might be the sound system pulling too much from the battery. Which causes the can-bus to not be able to send signals to other components. I kinda want to sell the car to get rid of the problem, but I don’t want to sell a faulty car. I might just try and not play loud music and hope it doesn’t come back.

It’s really annoying that in order to have a working car you have to restrict your volume or other stuff which draws power from the battery.

 

The battery cannot have a voltage of more than around 12.6 volts at rest. It is a physical impossibility. Any voltage above that is an indication that some charge is being applied*. Voltage is not a reliable indication of the amount of charge being applied, but the voltage has to be higher than the battery voltage to force it into accepting a charge. Normally a voltage around 14.7 volts is the highest safe voltage and indicates that the charger is charging the battery as quickly as is safe, but it does not tell you the actual SOC of the battery at the time.

But, these cars have a stop/start system with an "intelligent" alternator controlled by the battery monitoring system. Unlike a traditional automotive charging system, the amount of charge varies and is reduce or even stopped when the car is accelerating or under load on throttle, and increased when on the overrun or whilst braking, in part to reduce emissions by removing the charging load from the engine when it is using power elsewhere, and to make use of periods when it would otherwise be doing very little.

As part of that system, the battery is kept in a less than fully charged state, normally around 80%, to ensure that there is room for the generated charge to be accepted by the battery and not go to waste, increasing emissions for no good reason. That is why the cars are fitted with AGM or EFRB (enhanced flooded) batteries. They are designed to operate effectively and have a long life whilst predominantly in a less than fully charged condition - something that would cause a "normal" lead acid battery to fail prematurely.

* A phenomenon called surface charge will cause a battery to exhibit a slightly higher voltage than its standby or resting voltage for a period of time after it has been charged. The voltage will reduce to actual resting voltage over a period of a few hours when the battery is not being used, or can be removed by temporarily applying a heavy load.

 

This was a lot of gods information, thank you!

I drove my car today to test it, and when I drove up a mountain the speedometer and everything on the dashboard stopped working. When I got to the top I plugged in my reader and took that picture in my previous post. When I took off after around 15 minutes the speedometer worked, but it stopped working not long after.

The speedometer comes and goes, sometimes I loose my indicators and a lot of other stuff. I just changed my battery to an EFB battery. I don’t think it’s the battery which causes the problem, but the can-bus system. Which looks like a big hassle to debug. The only fault code I ever have gotten is “lost communication to body control module”. I’ve researched and it seems to have a lot of possible reasons to get that code.

Any good tips?

 

I assume the mention of "body control module" comes from a generic code reader or generic code lookup?

Volvo call it the Central Electronics Module (CEM), which is located behind the glove box in the passenger footwell.

A loss of communication with the CEM on one or more lines could have a number of causes, but as it is the location of two of the multi-pin connectors carrying network communications, which are known to suffer from connectivity issues on some cars as has already been mentioned, and which could easily result in the numerous intermittent and otherwise apparently unconnected issues that you are experiencing, investigating these has to be high on the list.

Have you already checked them? Start by disconnecting and reconnecting the plugs a few times with the ignition off. The action may in itself be enough to clean the contacts and restore a good connection. If not and/or corrosion is obvious, try cleaning the contacts carefully with judicious use of an electrical contact cleaner.

If none of this works, Volvo have a kit as mentioned in post #12 which replaces the connector pins with new gold plated pins. It requires the existing cables to be separated, carefully cut and soldered to the new fly cables and connected pins, then reinserted into the connectors, which is a time consuming but fairly straightforward job if followed carefully.

It does sound to me that this may be the likely cause of your issues.

 

So I plugged everything out of the cem except the green plug you slide out I think. It worked for a few days but the error codes came back, the dashboard stopped working . The same code as always “U0140”. It seems that everytime the voltage while the engine is running drops to around 13.5V the codes come up. When I don’t get the codes and everything works it stays at around 14.4V-14.7V. Today I caught the voltage drop from 14.5V to 13.5V and I saw the error codes pop up when it did.

It also seems to that the voltage drops shortly after the startup, but if it doesn’t then everything works until the next startup. Then it might do it again and the codes pop back up. I then have to erase the code and start the car back up for everything to work.

I really have no idea what the problem is anymore. But it almost seems that something draws voltage from the car, and when it does, that causes the voltage to drop and the car gets all the Error codes.

 

I tried to look at the cem, but I didn’t know what to look for and was scared to do something wrong, but I will try this. Thank you so much for your tips and knowledge <3

 

Hi guys, I'm resuming this discussion because I have the exact same problem as larskupen and I can't solve it. With a generic ob2 I can only see error U0140 related to loss of communication with the ECU module. Do you think there is a scanner that gives more detailed information?? Thank you