Sonata (2000), ABS and TCS Off lamps both on. Car drives and brakes normally.

Discussion in 'Hyundai Sonata' started by Tom, Jun 18, 2009.

  1. Tom

    Tom Guest

    Can anyone give me a techical reason why the 'ABS' and 'TCS Off'
    indicators have both become permanently illuminated on my Sonata V6 /
    2.5 (2000).

    The car seems to drive normally.

    I'm an experienced electronics engineer so happy to do some serious
    Tom, Jun 18, 2009
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  2. Tom

    Ed Pawlowski Guest

    It will drive normally, but if you need the abs, it won't be there. The
    brake systems are designed to function in normal mode if any electronics

    You may have a bad wheel sensor or some other malady. Hook up the diagnostic
    computer and get the code. Many auto parts will do it for you.
    Ed Pawlowski, Jun 19, 2009
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  3. Tom

    Tom Guest

    It will drive normally, but if you need the abs, it won't be there. The
    Fail-safe would make sense. I would like to understand the common
    elements of the ABS and the TCS that would cause my 'TCS-OFF' and
    'ABS' indicators to both become permanently illunmninated at the same

    The wheel sensor you mention - Could you tell me roughly where to
    locate it so I can trace its wiring ?

    Do you know what technology the sensor uses; magnet/hall-effect - reed

    Tom, Jun 19, 2009
  4. Tom

    Ed Pawlowski Guest

    The ABS and TCS use some parts in common. You can get more information as
    to location and so forth by signing up for a free account at You need IE and may have to download a free viewer from
    Adobe to see the drawings.
    Ed Pawlowski, Jun 19, 2009
  5. Tom

    Mike Marlow Guest

    Typically, it's part of the wheel bearing. Easy to see - there is a wire
    running to the bearing. Magnetic in nature, and it just creates a square
    wave pulse. The common elements are simply the sensor. Both ABS and TCS
    operate using the input from these sensors, one to prevent lock up and the
    other to attempt to maintain proper relationship between the rotation of
    each tire.

    The other day I picked up a nail or something in the inside sidewall of my
    passenger side front tire. Had to have another tire ordered in at the place
    where I purchased these tires. So, in the meantime, I drove around with the
    space saver spare mounted up there. ABS and TCS lights burning the entire
    time. Got the new tire mounted and poof - they were out. The space saver
    is a different size tire than the real stuff, so the wheel on that side is
    rolling at a different speed than the others. Throws the system off.
    Heck - even the speedo was off. It showed almost 10mph faster than what my
    GPS showed me traveling.
    Mike Marlow, Jun 19, 2009
  6. Tom

    hyundaitech Guest

    Typically, this would be the lack of any sort of input that would
    cause both the ABS and TCS to not be able to operate properly. If you
    make a couple panic stops, you'll see that the ABS is no longer
    functional. Both the ABS and TCS are controlled by the same module
    and actuators. Since you're an electronics engineer, you can probably
    infer a very good understanding of how the system works by consulting
    the schematic at as Edwin has suggested.

    Checking individual components and wiring until you find an issue is
    not an efficient way to go about solving this problem. There are
    simply too many possibilities. Normally, I'd suggest checking the
    wheel speed sensor tone wheels (on the axle or wheel hub) since it's
    quick to do if you can get under the car. But since you don't seem to
    have a good idea of what you'd be looking at, that's likely a futile
    exercise. The place to start is to take the car to a shop capable of
    diagnosing the ABS/TCS system. They'll read the codes and inspect the
    specific items that could potentially cause that particular code.
    Once you know the specific problem, you're in a better position to
    determine whether it's a repair you'll be able to do yourself.
    hyundaitech, Jun 21, 2009
  7. Tom

    Tom Guest

    Hmm, before I can put the oscilloscope on the wheel sensor signals I
    must get the schematic for the vehicle from HMASERVICE when I figure
    what my Sonata V6 2.5 (year 200) is in terms of the choice made
    available, vis:

    Sonata EF
    Sonata NF
    Sonata Y2
    Sonata Y3

    Then, I recall that one of the following links leads to schematics

    Tom, Jun 23, 2009
  8. Tom

    hyundaitech Guest

    Years 1999 to 2005 are Sonata EF. Once you choose one of the models,
    the page will delete all years which do not apply.

    The ETM (Electrical Troubleshooting Manual) leads to schematics. DTC
    = Diagnostic Trouble Codes. TSB = Techncial Service Bulletin,
    hyundaitech, Jun 24, 2009
  9. Tom

    Tom Guest

    Years 1999 to 2005 are Sonata EF. Once you choose one of the models,

    Thanks for that advice.

    Today, in an effort to obtain the CAN diagnostic error code I took the
    car to the garage only to be told by the service manager that
    hooking-up their diagnostic device would amount to 'at least an hour's
    work' - I didn't get the code today

    I have noticed that my TCS-OFF' and 'ABD' indicators only illuminate
    after the car has moved a few metres so there is perhaps a good
    indicator of a movement sensor input going on here.

    I obtained the schematics for the TYCS/ABS and once I have located the
    ABS module I will make some diagnostic measurements.

    Was interested to read one respondent refer to the toothed wheel part
    of the inductive pickup as a 'tone wheel' - a fellow Hammond player I
    thought! Correct tech!
    Tom, Jun 24, 2009
  10. Tom

    Tom Guest

    This afternoon I located the four wheel inductive pickups but their
    wiring disappears into a loom so I haven't located the ABS electronics
    module yet. Any suggestions of where it is to be found? I figure that
    this module is thelogical place for me to check all the wheel sensor
    Tom, Jun 25, 2009
  11. Tom

    Mike Marlow Guest

    Have you created a user account on the free Hyundai web site with all of the
    manuals, diagrams, etc. yet, as was suggested to you in reply to your
    initial question? You can flog yourself all day long, trying to muscle
    through this, or you can cheat and use some of the documentation that is
    provided to avoid a lot of that frustration.
    Mike Marlow, Jun 25, 2009
  12. Tom

    Tom Guest

    Have you created a user account on the free Hyundai web site with all of the...
    Yes, I registered with that site some years ago and have been using it
    tho' my Browsers (Firefox and IE8) are giving me so much trouble with
    Adobe's SVG format I'm finding it easier to trudge through the hard

    I haven't managed to get it to show me the whereabouts of the ABS
    module, Can you tell me?
    Tom, Jun 25, 2009
  13. Tom

    hyundaitech Guest

    You'll find the ABS/TCS module on the right side of the car near the
    firewall above the alternator.

    The fact that your car must move for the warning lamps to illuminate
    suggests that it's not a purely electrical issue, i.e. a resistance
    check won't turn it up. It could be a faulty signal-- are all your
    tires the same size?-- or a performance-test issue. The ABS/TCS
    performs a quick self-test shortly after the vehicle begins moving.
    hyundaitech, Jun 26, 2009
  14. Tom

    Tom Guest

    You'll find the ABS/TCS module on the right side of the car near the
    I am pretty sure I found it. A metal box with a group of brake pipes
    leading from one side, a 10cm diamter black motor visible to another
    side of the assembly and a substantial mutiway loom connector with a
    cunning retaining mechanism.

    I would like to get the pinout for that connector so I can check the
    various power and sensor signals are getting that far.
    I measured about 3.5k ohms on the front/right and front/left sensors
    but despite fishing about the boot/trunk, haven't managed to find
    those in-line connections yet.

    I checked the tyres, they seem ok. I guess the ABS/TCS computer has to
    allow some amount of wheel speed discrepency, at least for a short
    period, or perhaps at low speed. Otherwise they would set off the
    alarm on a tight radious manouvre such as parking, for instance?
    Ah, I wonder if that is what's happening, and that test is failing and
    bring on the 'TCS OFF' abd 'ABS' indicators?
    Tom, Jun 29, 2009
  15. Tom

    Tom Guest


    All the wheel sensors are two wire devices and all have in-line
    connectors just after their cable gromits bring their cable through
    the body to the inside of the vehicle. The rear connections are pretty
    hard to get at but accessed by folding down the rear seat back and
    unscrewing a two part flat’ish panel that runs along the back shelf
    and descends down on either side: This reveals the connections.

    I measured each sensor at just under 1.4k ohms.

    So starting the car and a short test drive and the ABS indicator is no
    longer illuminated.

    It’s looking to me like a connector/contact related problem. If I had
    to guess I would suggest the visible corrosion-like residue on the
    multiway connector fitted to the ABS control computer / actuator.

    Thanks to all on this helpful folk on this group for their assistance.
    Tom, Jun 30, 2009
  16. Tom

    hyundaitech Guest

    This is not a good development.

    There should be a seals in the ABS connector to keep water and
    contaminants out of the terminals. Once corrosion sets in, it's
    difficult to keep it away permanently. If this is indeed corrosion,
    try to clean it off as well as possible and make sure the seals on the
    connector and wires are in good condition.
    hyundaitech, Jul 1, 2009
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