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    ABS/PSM lights

    I get the ABS/PSM lights on heavy acceleration. When checked by the dealer(s) it shows a MAF problem. The Mass air sensor has been replaced twice, and the problem keeps coming back. The car runs fine, and the faults reset after turning off the ignition and restarting. Two separate dealerships can't figure it out. Was wondering if anyone else has had this problem and resolved it. I do have a remapped ECU, but not sure how that would affect it.

    Re: ABS/PSM lights

    When I started to read your post, I wanted immediately to ask you if you have a remapped ECU. What model year is your Turbo?

    I think the remapping hasn't been done right (if the dealerships you mentioned checked everything else and it seems OK). Maybe they used a ECU software which isn't fully compatible with your car. This happens mostly with so called mail-in ECU upgrades. I can almost bet that they didn't modify YOUR software on YOUR motronic but installed a different unit.

    Re: ABS/PSM lights

    RC
    I had Upsolute do the programming. They program the onboard chip. It is the same ECU unit, the chip is pulled, programmed and soldered back in place. I was wondering how the programming would throw a MAF fault. Any other areas to check?

    Re: ABS/PSM lights

    Oh sorry, its a July 01 build

    Re: ABS/PSM lights

    Well, it wouldn't be very wise to pull the chip to reprogram it. This is how it is done: they take a laptop, connect it to your motronic unit (usually they take it out) and reprogram the flash memory of the ECU. No pulling out of chips or any other parts. I know that some Tuners tell that to customers to justify the high price tag but this isn't true.
    It takes maximum one hour to adapt the mapping and upload it to the ECU unit (motronic). What might have gone wrong? Well, there are different software builds of Porsche's motronic software. Not all of them are fully compatible with each other.
    So if they used an early MY 2000 software for your remapping, this might be a problem. Again: MIGHT. I don't say that the remapping is the problem and I don't know the company you mentioned.

    My personal advise for anybody interested in ECU upgrades/tuning: don't fall for cheap offers or mail-in stuff (though some mail-in Tuners do the right thing...remapping the original software but this is not a perfect solution).
    Choose a well known Tuner who has experience with Porsche cars and also ask around to hear customer experiences.

    Yes, I know...so called "well known Porsche Tuners" ask a lot of money for remapping only. But it is worth the money if you want to have quality stuff. No to talk about possible reliability problems.

    Re: ABS/PSM lights

    Cobra,

    you may want to check the Rennlist board archives ...
    The PSM/ABS "problem" is not so uncommon. Usually it can
    be traced back to some kind of vaccuum problem: a leak in
    the line, extremely bad DV's or maybe an overboost (the list
    can get very long) Have you had the boost level checked?
    Shouldnt' trust your in-car boost indicator!

    I strongly suspect that the chip thing is to blame. MAF is
    probably NOT directly related to PSM/ABS. But it probably
    IS another indication of that something is wrong with the
    engine management. A relatively easy test: pull the chip,
    see if the problem is gone...

    You can email me privately if you have questions

    Re: ABS/PSM lights

    Dave,

    I had it occur once to me on track, and once to a friend of mine in a tip on track. i was using the track tires from my 993tt, and I seem to remember that some time ago a friend of mine had the same problem on a C2, and the dealer said that it had to do with mis-matched tire sizes (that the car only picks up on under certain circumstances, like on the track) as long as I was pushing the car hard and sliding it, the lights did not come on. The only time the ABS/PSM lights came on was when I was half "babying" the car. Could this be a possible explanation?

    -Konrad
    P.S. We could have tested this out more thouroughly at the track last Monday......

    Re: ABS/PSM lights

    Konrad,

    regarding your statement that you encountered PSM/ABS thing
    when "half-babying" the car at the track.

    Yes, the PSM/ABS condition tends to occur either at partial
    throttle or on lifting the throttle. I am not sure why: maybe
    this has to do with the boost vs. the airflow produced by
    turbos as a function of the throttle position?

    Regarding the wheel/tire sizes: I've seen this happenning
    with both the stock Pirelli Ass's and Michelin Pilot Cup's.
    Both are pretty evenly matched rear/front so I don't believe
    that was the issue.

    Re: ABS/PSM lights

    VS+

    Thanks for the feedback. The lights came on when I was using Hoosiers on my car, with the 285 rears. These are also pretty well matched. I have not had any problems with the car with stock tires (of course, I probably have never driven the car too hard on the street).

    On the chip, Cobra's chip is the original EEPROM that has been reprogrammed, so he can't really pull the chip out to do the test, only reprogram it with the stock program.


    Re: ABS/PSM lights

    The programmers thinks that the MAF is overshooting its assigned value, and an adjustmant to the file is needed. I was part of the Rennlist thread on PSM/ABS lights, and went through all of those possibilities. After exhausting those, it had to be programming. Anyone know why a MAF fault will trigger the PSM/ABS lights?

    Re: ABS/PSM lights

    Cobra,

    Question: does your car break loose with the boost on? In other words,
    just before the ABS/PSM thing happens, do you have to modulate gas
    to keep wheels from spinning?

    "Beware of programers with screwdrivers"




    Re: ABS/PSM lights

    No, it happens under hard acceleration, track/highway. When boost is @.9-1,1 BAR, in the 100 mph+ range, I never loose traction or brakes.
    I wish I understood the system better to know How these things are all related. Service adviser could not offer a good explanation.

     
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