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  1. #1
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    Default Volvo XC70 drivers low beam halogen headlight problem advanced

    Hi I recently purchased a 2007 XC70 2.5 T wagon with 115 K miles on it . One of the five messages was low beam failure. The drivers side low beam was out along with the rear passenger side parking light. Silly me thought it would be as simple as changing the burned out bulbs. Then I checked out the forums and read the many problems people have with the low beams...and here I thought the park assist and brake assist messages would be the hard part. lol So far I 1. checked the fuses and replaced two that were burned out, One was #16 for the drivers side low beam. unfortunately replacing it didn't fix the problem. I can't remember what the other fuse was for, it was 10amp. 2. tested the low beam by swapping with the passenger side. The halogen bulbs worked fine. 3. Replaced the burned out rear left parking light bulb and works now. 4. Replaced the socket. There didn't seem to be any heat damage but contacts seemed loose. Unfortunately this still didn't fix the problem. 4. Tested voltage at the socket and fuse of the drivers side low beam. One of the forums said not to use a multimeter because it can give strange readings. Of course I did it anyway. According to the multimeter there were 6v on the drivers side and 11.25v on the passenger side at fuse 16 and 17. The numbers bounced up and down alot. A 6 -12v meter lit up at both fuses but not at the socket. Can someone please tell me what to try next. The forums mention replacing a relay and or the CEM, or is it a relay on the CEM? I am learning as I go so please spell it out in as much detail a you can Thank you, Rick

  2. #2
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    Quote Originally Posted by rick 01034 View Post
    1. checked the fuses and replaced two that were burned out, One was #16 for the drivers side low beam. unfortunately replacing it didn't fix the problem.
    If a bulb shorts out and blows the fuse, a self diagnostic code can be stored and the CEM can/will prevent that circuit from working. Clearing the code restores power. I always used VIDA, so not sure if a generic scanner would pick up the codes.

    It also might be fixed with a "reboot" of the control units. Disconnect battery, hold battery cables together for a minute or two to drain all electrical energy from the car, then reconnect and see if that helped. There is not an external relay on the CEM for the headlamps.

    You will have to reset the auto up windows after battery disconnect.

    It's OK to use standard volt/ohm meters to help diagnose cars - but they can fool even the best tech.
    Last edited by hoonk; 06-20-2020 at 09:40 AM.

  3. #3
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    Quote Originally Posted by rick 01034 View Post
    Hi I recently purchased a 2007 XC70 2.5 T wagon with 115 K miles on it . One of the five messages was low beam failure. The drivers side low beam was out along with the rear passenger side parking light. Silly me thought it would be as simple as changing the burned out bulbs. Then I checked out the forums and read the many problems people have with the low beams...and here I thought the park assist and brake assist messages would be the hard part. lol So far I 1. checked the fuses and replaced two that were burned out, One was #16 for the drivers side low beam. unfortunately replacing it didn't fix the problem. I can't remember what the other fuse was for, it was 10amp. 2. tested the low beam by swapping with the passenger side. The halogen bulbs worked fine. 3. Replaced the burned out rear left parking light bulb and works now. 4. Replaced the socket. There didn't seem to be any heat damage but contacts seemed loose. Unfortunately this still didn't fix the problem. 4. Tested voltage at the socket and fuse of the drivers side low beam. One of the forums said not to use a multimeter because it can give strange readings. Of course I did it anyway. According to the multimeter there were 6v on the drivers side and 11.25v on the passenger side at fuse 16 and 17. The numbers bounced up and down alot. A 6 -12v meter lit up at both fuses but not at the socket. Can someone please tell me what to try next. The forums mention replacing a relay and or the CEM, or is it a relay on the CEM? I am learning as I go so please spell it out in as much detail a you can Thank you, Rick
    I have a wiring diagram for 2002 V70 and it shows the CEM drives a relay (CMI7) that goes to two fuses; fuse 18 goes to the LH drivers side low beam and fuse 17 goes to the RH passenger side low beam. My wiring diagram fuse numbers may be different than for your model year but I'll bet it's a single relay driving the low beams on both sides, which would rule out your CEM and relay since the passenger side low beam works okay. If you're measuring 6V at the fuse (or is this at the socket?) then that's a problem, especially if it's bouncing up and down. Multimeter should have no problem measuring the simple DC voltage. If the unstable 6V is being measured at the fuse box then there could be problem with the fuse contact or wiring from the CEM relay to the fuse box. If possible inspect the bottom side of the fuse box connections. I would expect the problem is there or at the fuse contacts or the fuse itself since the other low beam fuse voltage appears to be okay.

    If the 6V is being measured at the low beam socket and the voltage at the fuse is over 11V then you have resistance or poor connection between these two points. With power off you can measure continuity and any resistances between the fuse box and low beam socket. Check the fuse for any resistance and poor contact at the fuse contacts in the fuse box.
    Last edited by FirstVolvo; 06-20-2020 at 03:59 PM. Reason: spelling correction

  4. #4
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    Quote Originally Posted by FirstVolvo View Post
    wiring diagram for 2002 V70 and it shows the CEM drives a relay (CMI7) that goes to two fuses; fuse 18 goes to the LH drivers side low beam and fuse 17 goes to the RH passenger side low beam.
    I agree, on a 2002 xc70, relay 2/62 on the CEM powers BOTH left and right headlamp fuses. (And relay 2/63 powers both high beams) Maybe they changed because a bad relay would take out both low beams.

    Volvo changed the CEM design sometime around 2005 - early cars were a flat design, later CEMs had a 90 degree bend in them.

  5. #5
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    Hi Rick,

    I had a similar problem on my 2007 XC70. The driver's low beam was out and there was a warning light on the console - bulb failure, or something like that. No big deal, right? Seems like a simple thing to fix.
    Mine did not blow a fuse. The bulb seemed fine.
    I traced the wiring the best I could, checking that ground was to ground, that the other line was not ground back toward source, and that the resistance through the bulb was a few ohms.
    After resetting/clearing the codes, when I first turned the key the light would come on and then go immediately out. This could be seen in the garage where a wall in front would show that both bulbs were on briefly, then the driver's low beam would go out.
    A code reading showed that CEM-8A20 was set (Low Beam Left. Signal Too Low).
    Unfortunately, the problem was the CEM. Hopefully, your's is not.
    I sent it to XeMODeX and their tests showed that there was water corrosion on the head light circuit. They transferred my programming to a reconditioned unit, which I installed. Problem solved....at the cost of almost $700 USD.
    The CEM is not too hard to replace. If it comes to that, you can find a video on their site which shows you how to do it. Overall, I was pleased with their service, it's just very expensive.
    BrickDriver

  6. #6
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    Quote Originally Posted by FirstVolvo View Post
    I have a wiring diagram for 2002 V70 and it shows the CEM drives a relay (CMI7) that goes to two fuses; fuse 18 goes to the LH drivers side low beam and fuse 17 goes to the RH passenger side low beam. My wiring diagram fuse numbers may be different than for your model year but I'll bet it's a single relay driving the low beams on both sides, which would rule out your CEM and relay since the passenger side low beam works okay. If you're measuring 6V at the fuse (or is this at the socket?) then that's a problem, especially if it's bouncing up and down. Multimeter should have no problem measuring the simple DC voltage. If the unstable 6V is being measured at the fuse box then there could be problem with the fuse contact or wiring from the CEM relay to the fuse box. If possible inspect the bottom side of the fuse box connections. I would expect the problem is there or at the fuse contacts or the fuse itself since the other low beam fuse voltage appears to be okay.

    If the 6V is being measured at the low beam socket and the voltage at the fuse is over 11V then you have resistance or poor connection between these two points. With power off you can measure continuity and any resistances between the fuse box and low beam socket. Check the fuse for any resistance and poor contact at the fuse contacts in the fuse box.
    You may be right about there being one relay, though I have seen enough changes between model years, let alone between models to make me question it. That said I don't think I can eliminate the possibility of there being separate relays quite yet. It was 6 volts at fuse 16 (drivers low beam)and just over 11 volts at fuse 17 (passenger low beam). The readings fluctuated widely on both fuses but settled on these values most often. There was no voltage reading at the drivers side socket. I cleaned the fuse and contacts with fine sandpaper and swapped the fuses out to test them. I will try to inspect the bottom of the fuse box and measure the continuity and resistance from the fuse to the socket. Again I am not very experienced in the use of a multimeter. It was a more than a few years ago but I actually blew my last one/ first one out by having the settings wrong. Thank goodness for Harbor freight specials. I learned to look on u tube where I am sure there is a video to show me how this is done. If you are correct and it is not the relay or the CEM the only other possibility I have seen mentioned is the wiring harness though I am not sure what that includes. The other question I have is whether there are separate wires for each low beam on each side, or if the power is routed from the passenger side low beam over to the drivers side (Even if it is a separate wire)?

  7. #7
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    Quote Originally Posted by hoonk View Post
    I agree, on a 2002 xc70, relay 2/62 on the CEM powers BOTH left and right headlamp fuses. (And relay 2/63 powers both high beams) Maybe they changed because a bad relay would take out both low beams.

    Volvo changed the CEM design sometime around 2005 - early cars were a flat design, later CEMs had a 90 degree bend in them.
    This makes me both believe there is only one relay, and yet question it more. LOL

  8. #8
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    Quote Originally Posted by BrickDriver View Post
    Hi Rick,

    I had a similar problem on my 2007 XC70. The driver's low beam was out and there was a warning light on the console - bulb failure, or something like that. No big deal, right? Seems like a simple thing to fix.
    Mine did not blow a fuse. The bulb seemed fine.
    I traced the wiring the best I could, checking that ground was to ground, that the other line was not ground back toward source, and that the resistance through the bulb was a few ohms.
    After resetting/clearing the codes, when I first turned the key the light would come on and then go immediately out. This could be seen in the garage where a wall in front would show that both bulbs were on briefly, then the driver's low beam would go out.
    A code reading showed that CEM-8A20 was set (Low Beam Left. Signal Too Low).
    Unfortunately, the problem was the CEM. Hopefully, your's is not.
    I sent it to XeMODeX and their tests showed that there was water corrosion on the head light circuit. They transferred my programming to a reconditioned unit, which I installed. Problem solved....at the cost of almost $700 USD.
    The CEM is not too hard to replace. If it comes to that, you can find a video on their site which shows you how to do it. Overall, I was pleased with their service, it's just very expensive.
    BrickDriver
    When the check engine light came on I took it to an auto zone. I am not sure their reader would pick up all the codes.The only code it did read was for a loose gas cap. I didn't realize you had to close it till you heard the clicks. The light went out on its own after I tightened the cap and drove it for awhile. I wasn't aware that you had to have the programming copied over. I had read in another forum that it was 'plug and play" I too hope it is not the CEM but at this point I am so confused/frustrated that it would be good to just have an answer. Then I can fix it and get to the other issues so it will pass inspection.
    Last edited by rick 01034; 06-23-2020 at 10:08 AM. Reason: spelling correction

  9. #9
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    Not sure what I did but my reply to messages #2 and #3 aren't showing. I got a message saying it was going to the moderator and wouldn't be visible. I will wait to see what happens before resubmitting a reply.

  10. #10
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    Quote Originally Posted by rick 01034 View Post
    This makes me both believe there is only one relay, and yet question it more. LOL
    There is NO external relay on a 2007, There IS a relay for BOTH low beams on a 2002. What year is your car?

    Note the differences in the attached 02 and 07 diagrams. 02 has a low beam relay and uses fuses 17 and 18 for the low beams.(20 and 21 for the highs and a high beam relay) 07 has no relay and uses fuses 16 and 17 for the low beams and fuses 22 and 23 on the CEM for the high beams. The 07 CEM will turn off power (like a circuit breaker) to bulbs if shorted. Have you tried a reboot as mentioned earlier?

    Autozone scans for emissions codes - (to sell you emission repair parts) - you will need a scanner that will talk to a Volvo CEM.


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