550 ABS Hydraulic Control Unit Question? | FerrariChat
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550 ABS Hydraulic Control Unit Question?

Discussion in 'Technical Q&A' started by TimF40, Feb 2, 2006.

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  1. TimF40

    TimF40 Formula 3

    Nov 3, 2003
    1,035
    Seattle/Bay Area/NYC
    Full Name:
    Tim
    #1 TimF40, Feb 2, 2006
    Last edited by a moderator: Sep 7, 2017
    Earlier post recap: My ’99 550 amber ASR warning light comes on when some system is cold on startup. After the car and/or particular system is warm, the light stays off on startup and everything works fine. It started as being intermittent (when cold) to being solidly reproducible. I have no other warning lights, including the ABS.

    My dealer found out the cause of my cold-related ASR warning light: the ABS hydraulic control unit, to the tune of $4300! They are ordering the part now.

    The unit is item #11 in the attached picture. Various descriptions in the manual exist as to what the ASR and ABS units are, and how they coexist.

    From what I can tell, the ABS hydraulic control unit is the thing that carries out the physical modulation of the 4 brakes for the various purposes (braking due to ABS while stopping/wheel-locking or to car control due to ASR inputs).

    Anyway, what’s puzzling me is how can the ABS hydraulic control unit be bad just for the ASR, but okay for the ABS system?

    Are there separate ABS hydraulic control unit electrical connection inputs from the general ECU and some ASR specific unit someplace? The high level diagram suggests the one ECU connection into the ABS hydraulic control unit. What’s really the case?

    Are there ASR-only components in the ABS hydraulic control unit (that only the ASR logic communicates with)? The manual seems to indicate not, but obviously isn’t explicit.

    I’m paranoid that I’m replacing a $4300 part due to a simple cold solder joint problem or something like that outside the unit. However, I have great trust in my dealer – they seem to really know their stuff. I’m an engineer so I just have this need to have things make sense to me, and this one doesn’t yet. Hopefully you gearheads can set me straight.

    Any ideas or info, or places that might discuss this further?

    Thanks!

    Tim
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  2. dersark_painclinic

    dersark_painclinic Formula Junior

    Mar 8, 2005
    981
    Glendale, CA
    Full Name:
    Lazik Der Sarkissian
    #2 dersark_painclinic, Feb 2, 2006
    you may check with independent ferrari repair shops for trouble shooting since it is not a critical isue. I am sure your ASR switch is not on. check all wireing in the diagram nothing lose. $ 4300 what on earth they will do. I have a 99, 550 myself, yesterday while I was driving the suspension light came on, but after turning the engine off and on the light went off. I understand there are many lose conections with this car, check all the conections before you pay. good luck . please let us know.

    L. Der Sarkissian
     
  3. bobafett

    bobafett F1 Veteran

    Sep 28, 2002
    9,193
    #3 bobafett, Feb 2, 2006
    Personally I don't see how it makes sense.

    --Dan
     
  4. stephens

    stephens F1 Rookie
    Lifetime Rossa

    Feb 13, 2004
    4,647
    Australia
    Full Name:
    Stephen S
    #4 stephens, Feb 2, 2006
    I've just had a pedal box, dual master cylinder bypass ABS conversion completed. As a consequence I have a spare ABS unit.
     
  5. TimF40

    TimF40 Formula 3

    Nov 3, 2003
    1,035
    Seattle/Bay Area/NYC
    Full Name:
    Tim
    #5 TimF40, Feb 4, 2006
    Long story short: I asked them to go back and make sure the $4200 ABS hydraulic control unit part was indeed the cause of the problem. They did, and found that the ECU was bad instead. Problem fixed. The ECU was less expensive, but there was a lot more labor getting to that point. Ahem.

    Tim
     

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