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Thread: ABS Troubleshooting

  1. #1
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    Default ABS Troubleshooting

    I upgraded to Bear Claws and (with a little machining) was able to retain the ABS. Until recently it was working great but now my right rear locks up on hard braking with an ABS light. Does anybody know how to troubleshoot the system? So far my searches haven't borne any fruit. I'm thinking wheel sensor but I thought there was a procedure. Any help would be great.

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    yes there is a diagnostic connector to pull codes but do this......


    compare the toothed ring orientation to the brake sensor on the defective wheel to the left rear (compare condition)

    also, with the control module is turned off, your brakes work as normal power brakes.

    since its happening to one wheel, inspect the pads as well as the magnetic sensor parts back there.

    not sure what state your in, thinking debris may have built up causing the sensor to not act right.


    I havent done a write up on ABS T/S yet, doesnt really look all that bad though.

  3. #3
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    sorry, totally forgot to do this,, been a hard couple weeks at the cassity's.

    im away all week, this weekend ill dig something up.

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    No worries, I thought there was a connector under the deck lid that would flash codes but I couldn't find one. Surprised so few threads on the subject.

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    Check behind the mini spare cover, up by the driver's rear shock tower. Should like exactly like the EEC-IV OBDI connector.

    Might want to check out NATO's write up on the Teves II system. Jeff is a great guy who really knows his stuff:
    http://www.turbotbird.com/techinfo/T...7-88%20TCs.htm

  6. #6
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    Excellent article but doesn't delve into the ABS aspect of the system. I'll check the spare tire area for that connector. I assume you can jumper it and it will flash the ABS light. Hope codes are in my shop manual.

  7. #7
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    Found two ABS connectors near the spare tire that exit the bottom of the trunk. Are these the ones used to diagnose faults? I was expecting an OBD type connector.

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    Although you have an ABS light, I suspect that your trouble is purely mechanical.

    Shiny Side Up!
    Bill
    "as if 'religion' were something God invented, and not His statement to us of certain quite unalterable facts about His own nature." -C.S. Lewis

  9. #9
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    The diagnostic connector is up next to the ABS computer behind the rear seat. It looks like the engine diagnostic connector.

    Page 12-29 of the shop manual begins the trobleshooting according to the EVTM. I'd be looking for a mechanical issue first. I always start with the last thing I messed with.

  10. #10
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    87 shop manual
    Chassis Electrical Part 1 of 2, Vol B

    Page 12-32-1 starts the "Tbird" Anti Lock brake system consisting of 110 pages of component level troubleshooting.
    Page 12-32-21 shows the diagnostic connector and is located near the ABS module as already stated.

    At this time, this is what I have found.

    -Codes are pulled by way of a Star tester or a break out box.
    -I have not found a way to pull the codes directly from the diagnostic connector and I do not believe there is a known way at this time.
    -I have not found yet the wiring diagram for the break out box
    -No two codes with the same starting "Tens" digit can be stored at the same time.
    ---ie- code 21 and 24 can not be stored at the same time but codes 2x and 3x can be stored.
    -ABS can only store up to 7 codes at a given time. Fix one code the re-test to find more codes that are able to present themselves.
    -Once all codes have outputted and been serviced, the codes can only be erased by driving the car above 25mph.

    In order to figure out what diagnostic procedure to follow, it is probably best to compare the shop manual ABS warning lamp sequence of illumination as a guide to further pinpoint the next specific related troubleshooting step.
    IE- the time frames or frequency of the "Check Anti-Lock Brakes" and "Brake" warning lights.

    In various instances the "check abs" and "brake" warning lamps will illuminate but at certain times one lamp could be on while another is off.
    The shop manual does a good job of comparing the two lamps with respect to several operational aspects of the car and its situation such as cranking, starting, at idle, while braking ect.

    I will post this chart(s) up as well as a few other related pages to help on this aspect of our cars that has been neglected.
    Using the lamp illumination chart and comparing what lamp is on when, points to a specific troubleshooting step further in the the collective 110 pages dedicated to this subsystem component level troubleshooting.
    Since we do not know how to pull codes from the diagnostic connector like we do on the EEC, the only realistic and documented path is by way of using the warning lamp sequence chart.

    I have found the wiring diagram illustrating the harness from the ABS module out to all its sub components useful. It helps point to sensors which are called out with associated documentation calling out resistivity ranges and / or voltages to expect when a test is performed.

    What i would like to know is more information on the breakout box and if it simply intercepts the ABS harness wire for wire, pin for pin. This seems to be a reasonable application to a typical break out box since the ones Ive used did just that. It gives you a way to tap into the active harness while not poking at wiring.
    If the above is true, then we really do not need a break out box at all, as we all can poke at the wiring by using stick pins and get the same information.

    Hope this is helpful so far

    I will post and link the ABS scanned pages to the EVTM link soon, hopefully this weekend.
    Last edited by jcassity; 12-31-2010 at 09:04 PM.

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