1st Gen R53 Cooper S Ignition Switch causing Brake Light Issues?

Discussion in '1st Generation: 2002–06 R50, R53 & 2004–08 R52' started by xsmini, Jun 26, 2015.

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  1. xsmini

    xsmini Member

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    #1 xsmini, Jun 26, 2015
    So here is a new one for me, I hope someone can help. I spent some time this afternoon troubleshooting and am leaning toward the ignition switch,
    So the problem: turn the car off the brake lights come on (all three)
    What I checked: switch, brain in passenger foot well (checking for moisture, completely dry), traced the wires back looking for a diode I had read about, never found it, or any bad wires. When finished I started messing with the keys in the ignition. What I found. Turn car on, brake lights off, turn car on, brake light on, turn key to acc, and back off, lights off...

    Any ideas?

    Thanks,

    Nik
     
  2. rkw

    rkw Well-Known Member

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    #2 rkw, Jun 27, 2015
    The brake lights are not connected to the ignition switch, so the ignition itself is not the direct cause. However, it controls power to various modules and you may be seeing an indirect effect.

    All 3 brake lights are driven directly by the BCM (Body Control Module) in the passenger footwell. The brake lights are not driven by switches and relays, but directly by electronics in the BCM. Even the brake pedal switch merely sends a signal to the BCM, which actually controls the lights.

    Have you checked the switch at the brake pedal? However, I can't think of how a malfunctioning switch would cause the symptoms you describe. Your BCM might be going bad. By any chance, do you have the "rear fog mod" that makes the rear fogs operate as an extra set of brake lights? There is evidence that this mod can cause the BCM to fail prematurely.
     
  3. cristo

    cristo Well-Known Member

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    #3 cristo, Jun 27, 2015
    If doing the rear fog mod, it's a good idea to use LED lights in the fog position for
    this reason. This results in a minimal increase in current rather than doubling it.
     
  4. xsmini

    xsmini Member

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    #4 xsmini, Jun 27, 2015
    Yeah, these are weird symptoms. This is my 05 s with no modifications done to it at all. I did check the switch at the brake peddle, it's good, and I checked the BCM for moisture, it was bone dry and showed no signs of ever being wet. I was hoping for a cheaper fix than a new BCM.

    I appreciate the help, I don't do electronics well.

    Nik
     
  5. xsmini

    xsmini Member

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    #5 xsmini, Jun 27, 2015
    Oh, and the DSC light is always on now too. Related????:confused5:
     
  6. Metalman

    Metalman Well-Known Member
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    #6 Metalman, Jun 27, 2015
    And your battery is in "Good" shape?...
    When they start getting weak, strange things happen...

    You have a 2003 S and a 2005 S as well?
     
  7. ZippyNH

    ZippyNH Well-Known Member

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    #7 ZippyNH, Jun 27, 2015
    I' guessing yes....just guessing, but would make sense... one way the dsc would intervene would be brake application...
    The dsc might be seeing the brake lights on...saying brakes on? and faulting cause it has determined the signal to be false...so the dsc faults, since it has a signal coming in that it knows is false....
    Back when I had a t-map/map fail, the dsc came on...guessing it was a similar fault with the computer seeing data that was unreliable....
    Just a guess...but I'm thinking the dsc is a symptom....
     
  8. xsmini

    xsmini Member

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    #8 xsmini, Jun 27, 2015
    Yes, 03 has 355,000+ miles, the 05 has about 125,000, I had to sell my 74 a couple years ago :(

    Nik
     
  9. Metalman

    Metalman Well-Known Member
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    #9 Metalman, Jun 27, 2015
    WOW....

    I have an 09 and it just turned 24,000 miles... I'm doing something wrong...:cryin:
     
  10. ScottinBend

    ScottinBend Space Cowboy
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    #10 ScottinBend, Jun 27, 2015
    Let us know how old the battery is.
     
  11. Dave.0

    Dave.0 Helix & RMW Powered
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    #11 Dave.0, Jun 27, 2015
    New OEM BCM = $ 410.00 for just the part before programming.
     
  12. xsmini

    xsmini Member

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    #12 xsmini, Jun 27, 2015
    Battery is about a year old
     
  13. 00Mini

    00Mini Well-Known Member

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    #13 00Mini, Jun 27, 2015
    Ouch !! You definitely want to be sure that you need that part.
     
  14. xsmini

    xsmini Member

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    #14 xsmini, Jun 27, 2015
    What programming would be needed? Is it something that can be done and sent out? I live in BFE :biggrin5:

    Nik
     
  15. MCS02

    MCS02 Moderator
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    #15 MCS02, Jun 28, 2015
    The car has to go to the dealer I believe
     
  16. Dave.0

    Dave.0 Helix & RMW Powered
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    #16 Dave.0, Jun 28, 2015
    Nope you can't do it. The BCM needs to be coded to your car keys and everything else.

    I know Mike at Helix can do it if you are near Philly, PA.

    FYI we call anything West of Lancaster, PA BFE. :lol:

    Please check all your grounds especially the one under the hood by the upper motor mount. Check both ends and make sure they are clean and tight. Next have your battery tested or replace it with an Optima RedTop 34R. ($150-$200)

    All of these things are better then buying a BCM for $400 + install and programming at a dealer.
     
  17. ScottinBend

    ScottinBend Space Cowboy
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    #17 ScottinBend, Jun 28, 2015
    ^^^^ all of this,


    except the part about the Optima.......:D
     

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