Hello. This is my first post and sadly it's because I'm having so many issues with my beloved car. I've had my V40 for about 2 years and I've been very diligent about the normal maintenance (oil changes, tire rotation, turn ups, etc) but lately I've been experiencing issues that are beyond my ability to troubleshoot. Let me preface by saying that I am automobile mechanically deficient. I can build a computer from the ground up, but when it comes to cars...forget about it.

First, my check engine light came on, so I went to have it checked out. Was told it was firing out of order. They didn't give me the actual error codes, but I'm going to go back and get them so I can post them here. At that time, it was running just fine, no back fire, good acceleration, great speed.

Then, my headlights were turning off an on randomly. Thought it was the headlights, so changed them out, but nope Seems to be a connection issue in the CEM (at least from what I've read here). Sometimes, I can hit under the dash to the left of my steering wheel and one or both will come back on, only to go off a little later. Does the CEM seem correct? I don't know if there would be other things the CEM controls, but there aren't any other issues of that type; my blinkers work, my rear lights work, my running lights work, it's only my headlights.

And finally...every so often at at completely random times, my DSA light will come on, my car will start running rough and I will lose the ability to quickly accelerate. The car shakes really bad, but doesn't die. I can accelerate VERY slowly and then it will kick in to normal driving suddenly. Then sometimes, even tho the light will stay on, it will run just fine. Sometimes, I will go several days without this happening and then sometimes it will happen multiple times on several trips. It always clears out when I turn the car off and wait for 5 mins or so.

So, is my precious a goner? I have nearly $3500 in repairs into this car (had to completely redo the suspension due to hitting a grand canyon size pot hole in the dark, all new brakes and new tires). I probably should have scrapped it then, but it's in otherwise great shape and I just really like it.

Help? Suggestions? Talk to me like I'm dumb, because I will ask to have anything too confusing dumbed down anyway...

Thanks!!!

 

A few things here 1) go to Autozone etc and rent/borrow an OBD2 code reader and write down all the check engine codes. Easy DIY - the scanner plugs into a connector under the driver's side of the dash by the transmission hump (take a look for something that looks like an old school printer port connector). Plug the scanner in, turn the key to position 2 and follow the menus. Firing out of order makes no sense in an electronic ignition car so somebody probably misinterpreted the fault code. 2) For headlights, yes the low beams on the V40s goes through the CEM. Its a gray box right above the hood release lever under the drivers side dash. CEMS have relays that can fail or solder joints that can crack or connectors that can come loose. Start by pulling off the connectors and clean with electronics cleaner. If that doesn't fix it, find a local recycle yard for a CEM from a 2000-2004 S40 or V40. I replacement one for $65. hardest part of the job was getting the connectors off...(they pull off but you may need to work it with a flat blade). 3) the DSA light is the dynamic stability control which tells the ECU to cut engine power when it senses wheel spin. It gets its input from the ABS system which is fed by the wheel speed sensors. Sounds like you may have an issue with either the ABS controller (ever get an ABS light?), a wheel sensor, the DSA controller module or the wiring/connections. A quick fix would be to disconnect the DSA controller - I don't think that is required to run the car (but you'd lose the traction control and possibly the cruise control). You can also replace the ABS controller from a used car without opening up the ABS system and brake lines. Good news is the computer/controller modules on these models are not paired to the ECU so you can swap in a used part with no additional programming.

 

Thank you so much for the response and explaining so I understand. I am going to try what you've suggested this weekend and hope it's just a good cleaning.

I also didn't think that the firing out of order made sense. I've had cars that weren't firing correctly and they ran like crap. So I will go get it checked again.

I have gone thru 2 winters so far and never used the DSA, so if all it takes is unhooking it and not having it, then I'm fine with that. It happens so randomly that it's frustrating. It was fine all day yesterday and so far today.

Thank you for the info. I'm glad there might be hope. I've owned cars in the past, but genuinely love this one. So much so, that I'm going to get my daughter a Volvo after winter.

 

The 4 cyl engines only have two coils - each coil fires two spark plugs and the spark plugs fire every revolution, instead of only on the power stroke, or every 2nd revolution. They can miss fire - due to worn out plugs, arcing spark plug wires or coils.

And yes the CEM can go bad and not send power to the headlamps, usually the right one.

 

+1 on the coils - the wiring harness from the firewall to the coils can also develop cracks in the connectors so its a good idea to inspect both the wires (not an expensive replacement given there's only two) and the electrical connectors to the coils. Doing the OBD2 code scan will show if the ECU detected any misfires and may also identify which cylinder is at fault (ie a P0303 fault indicates a misfire on cylinder three (3rd from the timing belt side of the engine). P0300 is generic, P0301 is cylinder 1... P0304 is cylinder 4. PS - Plugs should be replaced every 60K miles or so - and no need to use expensive "triple iridium blah blah blah" plugs. OEM plugs work fine and come pregapped and are not that expensive. If you are not sure when they were last changed, spend the $25 to freshen up. If you are not sure of how old the plug wires are, look for a date code on the rubber. Older than 5 years = time to replace. Parts are easy to find at either a dealer store or a Volvo friendly web store like IPD USA (right there in Portland). I've also used Rock Auto and AZ Autohaus on the west coast and Tasca Parts (dealer) and FCP Euro (my top choice since they are about 20 miles from me so I get next day delivery for free).

 

My right headlight is the one that initially went out, but then my left one went too. They will randomly work, but then go off, so can't risk driving at night.

Quick question, where is the CEM located? In all the videos I can find, it's under the dash on the passenger side. From what I keep reading (and where I hit to try to get then on), it's to the left of the steering wheel under the dash. I'm going to take it out today and give it a good cleaning and see if that will help.

I'm going to give it a tune up next weekend. What all do you suggest changing? Plugs and wires? Anything else?

Thanks again for all the help and info.

 

As you said left of the steering wheel under the dash. It looks like the attached picture - and "cleaning it" will not be useful - what you need to do is replace the headlamp relays inside it -

 

Ok, thank you very much. Off to get some relays!

 

Seriously? - do you work on laptops or something for a living?

 

Not sure about the 'seriously' part, but no. I do not. I'm self-taught in computers, they are fairly straightforward. Cars, not so much. You have to take apart this, to get to that and then it might be 1 of 23 things that would be causing each issue. Computers are pretty easy to troubleshoot and a heck of a lot easier to fix.

Found the CEM, took it out and attempted to take it apart, but had a heck of a time. However, it started to downpour and I didn't want to risk any electronic stuff getting wet, so put everything back together and my right headlight is working now. Left headlight might be on, but could be very dim. I'm going to check when it gets dark. But at least there is hope.

 

Sure, same here since the early 90's. Unix servers, networking 2 shops to one server, dual networks in the same building (unix and windows) then moving to a windows server (unfortunately) and dealing with the problems of about 13 windows cpus -

But I would never try to fix a CEM. Just not worth the learning curve to me.

 

I only planned on cleaning the connections, since that is what was suggested. Also, several of the videos I've found recommend the same thing. My right light seemed to stay on for awhile, but then as i parked the car, it dimmed and eventually went off again. So, I'm going to just replace the CEM. I found one for $75 that has a 60 day warranty on it, so I'm going to do that for now.

 

Well, it was fun while it lasted. I got another CEM and my lights worked for a few days before the right one going out. The left one seemed steadily on, but tonight driving home (in the dark), it went off and wouldn't come back on. So now I'm not sure if it's worth all the money I've put into it. As much as I love the car, I don't have the money to pay someone to figure it out and fix it, nor do I have the know how to keep it up. On the plus side, it's gotten new tires all around, new front and back breaks and the entire suspension system is less than 2 years old.

Thank you all for the help.

 

So did your "another CEM" turn out to be a used part? You had a used bad one to begin with - and CEM failure of the headlamps is a known/common problem. All you did was put in another bad part. Contact someone like xemodex, get a fixed CEM and the problem will be solved.

 

Bought used because I can't afford another $700 for new. I've put nearly $4k into a car that is worth half that already. Thank you.

 

a fixed/good/working one from xemodex is $350 plus shipping - and one of your post said you were getting one from ebay with a warranty. Can't you return the bad one and get your money back? making the xemodex part $75 cheaper?

https://xemodex.com/us/product/centr...epair-service/

 

the Gen 1 S40/V40 CEMs don't need to be paired - and a used part can be found for about $75. You can find a local yard with S40s via car-part.com if you don't want to go the Xemodex route. With that said, the CEM is not always the cause for the headlights going out. Did you do the usual due diligence - ie check bulbs, fuses, power to the fuses (to make sure the dash switch is ok), power to the bulb connectors? Hate to pay 350 for a rebuilt CEM only to find you there's a wiring issue...