Need help diagnosing high speed CAN bus problem on '04 XC70
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    1. #1
      Junior Member
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      Need help diagnosing high speed CAN bus problem on '04 XC70

      I've been struggling with this issue for some time (posted back in April, but I have more information now), and I'd appreciate any help anyone can offer. Occasionally, like once every few months, everything on the high-speed CAN bus fails to communicate for a while. If it happens while the car is stopped, it won't crank. Using the iCarSoft tool, it says it cannot communicate with the ECM, CEM (high speed side), BCM, and TCM. If it happens while the car is running, all the gauges go dead, AC and cruise don't work, but the car will drive until you turn it off. Same deal with the iCarSoft tool -- it can't talk to the high-speed CAN bus stuff, doesn't even detect it is there. Then, if I let it sit a few hours or days, it would work like normal after that. The modules reported "communication failure" trouble codes, and sometimes random other codes that don't seem to be actual problems, like brake pedal sensor or immobilizer antenna (replaced both of those, no effect). I took it to several dealers but somehow the problem had always gone away by the time they got to it. I replaced the BCM and had the ECM and TCM checked by Xemodex, who said they were fine. I had the CEM upgraded by Xemodex to their heat-resistant version (I live in Alabama), but they said they could find nothing wrong with it. One thing that has worked recently to get it going when this happens is to either jiggle the ECM (in the box beside the power steering reservoir) or remove and re-seat the ECM with the special Volvo tool. Then it will generally start, again just reporting communication failures if you read trouble codes from the modules. My current hypothesis is that the socket for the ECM is the culprit. This seems very difficult to replace given that the wiring goes everywhere from that socket. Any ideas on how to improve the socket-module connection? Or any other suggestions for a diagnosis that matches these symptoms? Thanks!

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    3. #2
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      Can you post a recent VIDA screenshot with the error codes you get?

    4. #3
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      I don't have VIDA, just the iCarSoft tool, which does report Volvo-specific codes by module. Regarding VIDA, is there a cost-effective way to get the right tool and software? I see devices on Amazon and ebay, virtual ma chine images, and I understand you can buy the software for a couple of days for not too much, but I've never been able to figure the whole VIDA thing out. First question: what device to buy? Right now it is not giving any codes; I will take post the error codes the next time it gives them.

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    6. #4
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      I've got my DiCE clone long ago, in 2010 or 11. Would guess, any clone is good as far as the seller accepts the returns.

      Last "community" version of VIDA, 2014D, supports vehicles up to and including MY2015. It will read/reset codes/run adaptations/tests on any P2 vehicle without subscription. The software comes on DVD with the DiCE clone, or, if you don't trust Chinese viruses, get a VM image or download sw from torrent.

    7. #5
      Junior Member
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      Most of the discussion and free download sources for VIDA are in this thread here at Swedespeed:
      https://forums.swedespeed.com/forumd...ine-Management
      Read this sub-thread, and you'll practically have a PhD on the subject (and have earned it !)
      https://forums.swedespeed.com/showth...-Download-Link
      It's worth doing.
      2009 XC90 FWD 3.2, 2013 S60 T5
      In the past: '89 745, '91 940, '82 242, '67 122S, '67 123GT, '71 142E, '62 PV544.

    8. #6
      Junior Member
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      You are going to need VIDA to diagnose this problem, no way around it.

      When you are removing the ECM you are effectively hard resetting that module. If you want to try and throw parts at it you could replace just the CAN female pins in the ECM and TCM connectors.
      04 V70R Flash Green/Atacama6MT

    9. #7
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      Don't listen much to repair advises that people are giving here, me including. Until you get DiCE/VIDA and read the codes it will be virtually impossible to diagnose your issue properly. You see a problem on that picture of why the CEM in my car was loosing all the modules on high-speed CAN bus?



      No, my hand is not the problem. The problem is 1/32" small CMD resistor in DEM (differential module): water has penetrated into DEM, corroded one pad on that resistor, misbehaving DEM knocked the whole CAN bus out.

      So read the codes first.

    10. #8
      Junior Member
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      Were you getting a DEM code? How did you find the resistor? Presently the DEM is not reporting any codes (I do get the Volvo-specific codes from the iCarSoft tool, but I just ordered a VIDA /DiCE device from China)

    11. #9
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      I was getting DEM communication error, as well as in the rest of the modules sitting on the same bus. Pulling the DEM fuse did little, since the resistor was a termination resistor, as it seems (I didn't check), so the bus was full of signal reflection noise. The issue did stop only after I physically pulled the plug out of DEM.

      This may be a good reading (it was for me): http://www.s80.dk/Billeder/2010-05-26_205437_088051.pdf

    12. #10
      Junior Member
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      This response may be moot, but shortly after I got my car I had significant issues with what I believe turned out to be CANBus communication problems, which manifested in a similar manner as you described. I didn't know as much about the car then as I do now (and didn't have VIDA back then either, or any code readers), but the shop I used tracked the issue back to a failing relay, which they said was so hot they couldn't touch it. Since replacing it I haven't had any issues whatsoever in the 2 years or so since. I don't know if the same will work for you, but hey, anything might be the culprit with these electrical problems.

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