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Thread: CX-9 Body Control Module (BCM) failure

  1. #1
    Former CX-9 Owner

    CX-9

    Join Date
    Jan 2009
    Location
    Loveland, Ohio
    Posts
    2

    CX-9 Body Control Module (BCM) failure

    Hello
    I purchased my 2008 CX-9 Touring in July of 2008.
    In August I installed an aftermarket trailer hitch and a plug-in Draw-tite wiring kit. It all worked fine. In October I accidentally left the moon roof open over night and the interior was rained on rather heavily. When I started the car up to move it indoors to dry out I noticed an electrical burning odor and some things stopped working. I found the fuse for the turn signals blown. I replaced it and it did not blow again. I took it to the dealer and they instantly said my trailer wiring was at fault and no warranty applied. They did not test anything. They just assumed. I chose to fix this myself. I bought the manuals from Mazda. I quickly found that the Body Control Module (BCM) is not functioning. This kills the turn signals, door locks and interior overhead lights among other things. I also have a few incorrect lights on the dash. I checked the turn signal wiring and it is not shorted with or without the trailer wiring plugged in. I am an automation engineer and I wire things for a living. I checked the turn signal circuit by putting voltage on the output of the BCM and they seem to function fine with and without the trailer wiring plugged in.
    I hesitate to plug in a new BCM since I haven't yet been able to determine what killed the old one. I assume it had something to do with the water.
    Any similar experiences or suggestions?
    Thanks.....Frank

  2. #2
    2008 Mazda CX-9 GT

    Mazda CX-9 2008

    Join Date
    Jan 2009
    Posts
    2
    Frank,

    Where did you buy the CX-9 manuals from?

    I would assume these include the wiring diagrams and information on the buses connecting to the BCM, etc.

    Thanks.

  3. #3
    Registered Member OMF's Avatar

    2007 CX-9 GT AWD

    Join Date
    Apr 2007
    Location
    Ontario
    Posts
    159

    2007 CX-9 BCM Inspection (Set #1)

    Just in case you want to inspect your BCM...

    Note: this is 2007 model year!
    Attached Files Attached Files

    2007 CX-9 GT AWD; Rev B DVD Map Navigation

  4. #4
    Registered Member OMF's Avatar

    2007 CX-9 GT AWD

    Join Date
    Apr 2007
    Location
    Ontario
    Posts
    159

    2007 CX-9 BCM Inspection (Set #2)

    Set #2

    Good luck!
    Attached Files Attached Files
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  5. #5
    Registered Member

    2012 CX-9 Touring

    Join Date
    Mar 2017
    Location
    New York, NY
    Posts
    23
    Reviving this from the zombie dead.

    Thanks. The docs helped with a swap after the sunroof draines showered the BCM.

    My replacement was an eBay part and one plugged in we checked all we could.

    All the button beeps returned, need to figure out how to disable that.

    All in all of this fixes the sticky parking light problem I'll be very happy

  6. #6
    Registered Member

    CX-9 2013 AWD

    Join Date
    Jul 2015
    Location
    NY
    Posts
    329
    Quote Originally Posted by HobokenSkier View Post
    Reviving this from the zombie dead.

    Thanks. The docs helped with a swap after the sunroof draines showered the BCM.

    My replacement was an eBay part and one plugged in we checked all we could.

    All the button beeps returned, need to figure out how to disable that.

    All in all of this fixes the sticky parking light problem I'll be very happy
    glad it worked out for you, how did the sunroof drains soak the BCM ? I keep hearing of this issue but can't see how this happens if the sunroof is closed , does it only happen to owners who leaves their sunroofs open on nice days and tree leaves clog the drain and the rain water just starts collecting and soaks the BCM ?

  7. #7
    Registered Member

    2012 CX-9 Touring

    Join Date
    Mar 2017
    Location
    New York, NY
    Posts
    23
    Quote Originally Posted by astriuminc View Post
    glad it worked out for you, how did the sunroof drains soak the BCM ? I keep hearing of this issue but can't see how this happens if the sunroof is closed , does it only happen to owners who leaves their sunroofs open on nice days and tree leaves clog the drain and the rain water just starts collecting and soaks the BCM ?
    The drains don't.

    This car is parked outside on a tree lined street. My understanding is the dirt clogs the drain lines. A blast of compresses air helps keep them clean.

    Also I understand the sunroof seals are not watertight but water resistant so in heavy rain water gets into the drain areas.

    So the drain gets clogged. The water weeps around the connection and down the outside of the hoses to then get the footwells wet and the driver side kick wall wet. That's where all BCM connections in the car live.

    Water plus electronics and the gremlins move in.

  8. #8
    Registered Member

    Mazda

    Join Date
    Jun 2017
    Location
    Nutley, NJ
    Posts
    1
    Just replaced my bcm on my 2012 Mazda CX-9.
    Everything is back to normal. It took about one hour to carefully remove connectors with flat screwdriver and there was 2 screws holding bcm to car body.
    I paid for bcm $382+tax at Mazda parts in Wayne NJ.

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