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Thread: CEM-1a5e and CEM-1a5f, lots of warning lights

  1. #1
    Join Date
    Feb 2015
    Location
    NC
    Posts
    53

    Default CEM-1a5e and CEM-1a5f, lots of warning lights

    I had trouble finding any information online about this scenario, so I thought I would document my troubleshooting here in case someone else runs into the same thing.

    My '04 XC70 started throwing "missing signal" codes for the BCM and SAS modules, along with a brake pedal switch code. This is causing the dash to light up like a Christmas tree, threatening impending doom to the driver. The car still drives fine, but the ABS and DSTC appear to be disabled so I want to get it resolved. Interesting side note, the transmission actually seems to behave better with ABS and DSTC disabled. It normally exhibits some odd shifting behavior at times, which has gone away at the moment.

    My BCM module is a Xemodex rebuilt unit. The SAS module has never been touched. In 2016 I did open the CEM and install some heatsinks as a preventative measure. VIDA is unable to communicate with either the BCM or SAS modules. I found the pin specifications for the SAS module in the VIDA information records and checked the voltage at the power supply pin #2 with a multimeter, against the ground pin #16. Nothing... Just to be sure I was doing it right I checked the low speed CANBus pin and it had the expected 2.5v or so, checked against the same ground pin.

    Then I found this https://xemodex.com/us/knowledgebase...art-2002-2004/ , which recommends changing the 2 power relays on the CEM if the scan tool is unable to communicate with the module.

    Based on the Xemodex flow chart and the fact that I could not find any 12v power going to the SAS at the expected pin, I've ordered the 2 relays from FCP Euro. We'll see what happens after that. Stay tuned...

  2. #2
    Join Date
    Dec 2009
    Location
    GA
    Posts
    1,071

    Default

    Quote Originally Posted by brenglxc70 View Post
    I've ordered the 2 relays from FCP Euro. We'll see what happens after that.
    Most of those relays on the CEM are the same, you could just swap them with others and see what happens rather than waiting.

  3. #3
    Join Date
    Feb 2015
    Location
    NC
    Posts
    53

    Default

    my parts should arrive tomorrow. The 2 in question are different than the others on the board.

  4. #4
    Join Date
    Feb 2015
    Location
    NC
    Posts
    53

    Default

    It would appear that the relays solved the issue, the codes have not returned since swapping them. Where the BCM and SAS modules were greyed out in VIDA before and it couldn't communicate with them, now they are green and I can read parameters from them.
    Hopefully this will be useful for someone else before they drop big bucks on a CEM.

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