ABS fault weirdness

Discussion in 'GS Boxers' started by spagthorpe, Sep 20, 2012.

  1. spagthorpe

    spagthorpe Long timer

    Joined:
    Aug 9, 2002
    Oddometer:
    15,195
    Location:
    San Diego
    I've been having some weird ABS faults on a 2006 1150GSA, integral brakes.

    Bike will usually start and ride off with no faults. At some point in the ride, the general warning and fast flash brake light will come on. The first time, the GS911 reported 'front pressure too low' and 'defective front brake switch'. I cleared them. Did it again the next day. I didn't bother clearing. Both times, the servos are still working. I am assuming the ABS is off though.

    Today, I get the same error lights, but this time, no servos which was a surprise. When I got home and checked the codes though, it said 'rear pressure was low'.

    I could hear the front brake switch clicking, with my ear next to it. When I had the ignition on (bike not running) while hooked up to the GS911, I was playing with the front brake, and after a handful of pulls, the pump whiring stayed on, and I had to kill it with the key.

    Any ideas where to start? Obviously taking it anywhere with the brakes in random behavior mode is out.
    #1
  2. JimVonBaden

    JimVonBaden "Cool" Aid!

    Joined:
    Feb 11, 2005
    Oddometer:
    64,826
    Location:
    Alexandria, VA
    Have you dropped it recently? How long ago did you change your brake pads? It sounds like a low fluid issue with the reservoir under the tank.

    Jim :brow
    #2
  3. spagthorpe

    spagthorpe Long timer

    Joined:
    Aug 9, 2002
    Oddometer:
    15,195
    Location:
    San Diego
    Zero drops. I haven't pulled the tank yet to look at the fluid level.
    #3
  4. spagthorpe

    spagthorpe Long timer

    Joined:
    Aug 9, 2002
    Oddometer:
    15,195
    Location:
    San Diego
    I pulled the tank and looked at the levels in the front and rear. The front was up to the little white ring at the bottom of the fill chamber. The rear was a little higher than that. Looking at the ABS3 service PDF, this would appear to be at max so it doesn't look like the level is down. Just for fun, I turned on the ignition, and hit the brakes to see what would happen. I could see the level of the front go down slightly when applied, maybe a mm. Doesn't look like it's lacking for fluid.

    So if there is really not enough pressure, then that would mean the servo itself isn't generating enough. Seems weird that you could get the same error at both front and rear at different times unless there was something similar to both. I'm guessing the power for both servos is coming off a main circuit board? Some sort of relays for both? They power up fine, and I hear the whine, sounds normal.

    The bike only has 9,000 miles, and while I realize that some people have had faults early in the life of the units, still seems odd.
    #4
  5. JimVonBaden

    JimVonBaden "Cool" Aid!

    Joined:
    Feb 11, 2005
    Oddometer:
    64,826
    Location:
    Alexandria, VA
    Definitely odd. Probably not the battery, but it would be worth a full charge and a test.

    Other intermittant issues come from the sensors front and back.

    Jim :brow
    #5
  6. spagthorpe

    spagthorpe Long timer

    Joined:
    Aug 9, 2002
    Oddometer:
    15,195
    Location:
    San Diego
    About a week after getting it, I went to start it, and had some issues. The battery was likely original. I replaced it with an Odessey that week and everything fires up instantly now.

    Is there any way to test the sensors? I looked today, and didn't see any frayed wires or anything. Everything looks new.
    #6
  7. spagthorpe

    spagthorpe Long timer

    Joined:
    Aug 9, 2002
    Oddometer:
    15,195
    Location:
    San Diego
    Trying to understand how the ABS system "thinks" here. When I first start out on the bike, I never have any immediate errors. All warning lights off. This goes for 10 or so minutes into a ride, and THEN I get the errors. When the errors happen, I'm not doing anything but riding.

    I would assume that the system pressure is scanned at some interval, definitely at startup, and surely faster than 10+ minutes.

    Today, rather than just putting around town, I made sure that I was on it the whole time, keeping the rpms up high, worried that maybe my system isn't charging, and I'm getting the fault because the voltage is getting low as I'm riding. When I got home, I measured at one of the accessory ports and got 12.74V. This seems like it would be acceptable for the battery without the bike running, but if I was just coming back from a ride, I sort of would have thought the battery might still be coming off a charge but I'm not an expert on this. I also wasn't out long, as once the error happens, I lose all serve assist.
    #7
  8. batoutoflahonda

    batoutoflahonda Long timer

    Joined:
    Aug 8, 2007
    Oddometer:
    1,405
    Location:
    Easton Wa
    #8
  9. bone13

    bone13 Been here awhile

    Joined:
    Aug 23, 2009
    Oddometer:
    288
    Location:
    Knoxville, TN
    Whens the last time you changed the brake fluid?
    If it's been more than two years, try replacing the fluid.

    Old fluid can cause all kinds of ABS fault weirdness.
    #9
  10. Pedrogomezrios

    Pedrogomezrios Quiet

    Joined:
    Aug 18, 2012
    Oddometer:
    28
    Location:
    MedellĂ­n, Colombia
    as I said my r 1200 gs adv has the same problem, as soon as I took it to the dealer they said that the pressure modulator was broken, It casually started failing a soon as I picked it after the 40000 km service, my dealer recommendation was to change the modulator which cost around 2000 dollars, i have not done it yet. Do you think that i should change it, or look if something else is not working properly? and its this a common issue in this motorcycles because it seems weird to me that it stopped working right after i took it out of my dealers workshop?

    PS: sorry for bad English its not my mother language
    #10
  11. def

    def Ginger th wonder dog

    Joined:
    Feb 28, 2004
    Oddometer:
    13,561
    Location:
    The woods and mountains of Alabama
    #11
  12. spagthorpe

    spagthorpe Long timer

    Joined:
    Aug 9, 2002
    Oddometer:
    15,195
    Location:
    San Diego
    Oops. Meant to reply to this one...

    I actually talked to Modulemaster today. They are not taking any of our units right now. They are seeing a lot of the same parts, and have no source for things like the pressure sensor boards. They have in the past had some core units to cannibalize from, but not now. They are in the process of getting bids from some companies to make replacement parts like the pressure sensors, misc seals, etc. They think they'll be up and running with this all around January. It's a long time if you don't have a working unit.

    If my plans tomorrow don't work out with my own, I have no choice but to pull the unit and connect the brakes up old school. I know there is an issue with the brake switches, but I was wondering if anyone had tried one of these rather than spending $100 on BMW switches....

    http://www.bajadesigns.com/ProductDetail?ItemNumber=120100
    #12