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Thread: Abs light is on

  1. #1
    Member rtaylor231's Avatar
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    Abs light is on

    100% brand new braking system including all ABS sensors, all hard lines and all rubber lines , properly bled out and ABS light is still on. Any thoughts on this will be appreciated!! Thx everyone. This is on a 1998 JGC 5.2
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    How do the abs wheel speed sensors look?

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    Member rtaylor231's Avatar
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    Brand new!
    White 98 limited 5.9 (NOT A 5.9 LIMITED) Magnaflow cat and cat back, Edelbrock ceramic coated headers, Edelbrock aluminum heads, Meziere electric water pump, Spal HP 16" E-Fan, Spal fan controller, Comp cam 20-746-9, mopar 1.7 roller rockers, custom set of timing gears, steel under drive pulley for the crank, single plane mpi intake, Holley 52mm TB, accel cap, rotor, and coil, Taylor 10.5 wires, SCT tune, 180 thermostat, Spectre twin 4" cold air kit, and enough 1/0 gauge cable under the hood to run a small factory!

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    Oh sorry I missed that.

    I wouldn't worry about it, abs sucks

    maybe someone else can shed some light

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    Member rtaylor231's Avatar
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    Quote Originally Posted by MurdaJ View Post
    Oh sorry I missed that.

    I wouldn't worry about it, abs sucks

    maybe someone else can shed some light
    Honestly can't say in "worried" about it, but I would like it to function correctly. Although I do prefer no ABS!
    White 98 limited 5.9 (NOT A 5.9 LIMITED) Magnaflow cat and cat back, Edelbrock ceramic coated headers, Edelbrock aluminum heads, Meziere electric water pump, Spal HP 16" E-Fan, Spal fan controller, Comp cam 20-746-9, mopar 1.7 roller rockers, custom set of timing gears, steel under drive pulley for the crank, single plane mpi intake, Holley 52mm TB, accel cap, rotor, and coil, Taylor 10.5 wires, SCT tune, 180 thermostat, Spectre twin 4" cold air kit, and enough 1/0 gauge cable under the hood to run a small factory!

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    Forum CONDUCTOR Man Z88Z's Avatar
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    I don't know too much about ABS - but that won't stop me from giving it a shot! LOL


    Is it on right from startup or does it come on when you're driving? If it comes right on I guess that means it's failing it's self test, meaning most likely some circuit isn't complete.


    Did the system go dry at all when you were doing the lines, and how did you bleed it? I'm honestly not sure how much that has to do with anything though.

    I'm guessing you checked all the fuses. Besides the big one I'm pretty sure there's one or two smaller ones that tie into that system too.


    Assuming fuses are good, etc. only two things I can suggest...


    Make sure the new sensors aren't defective.
    Plug the old sensors in one at a time (check the connector and pins while you're doing it but they seem to hold up pretty well)
    Just do it at the inner fender or under the back seat - making sure the body of the sensor isn't near any metal. Then turn the Jeep on and see if the light stays off, which would point to a bad sensor.

    I should say I have no idea if there's any "memory" involved here, something that might be need to be re-set by discoing the battery - maybe someone can answer that? Couldn't hurt to try it between sensor swaps though.


    Other than that I'd say you'd probably have to pay someone to hook it up to a scanner.

    I know a lot of the auto parts chains do free CEL scans, but I don't think they do ABS scans for free

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    Member rtaylor231's Avatar
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    Quote Originally Posted by Z88Z View Post
    I don't know too much about ABS - but that won't stop me from giving it a shot! LOL


    Is it on right from startup or does it come on when you're driving? If it comes right on I guess that means it's failing it's self test, meaning most likely some circuit isn't complete.


    Did the system go dry at all when you were doing the lines, and how did you bleed it? I'm honestly not sure how much that has to do with anything though.

    I'm guessing you checked all the fuses. Besides the big one I'm pretty sure there's one or two smaller ones that tie into that system too.


    Assuming fuses are good, etc. only two things I can suggest...


    Make sure the new sensors aren't defective.
    Plug the old sensors in one at a time (check the connector and pins while you're doing it but they seem to hold up pretty well)
    Just do it at the inner fender or under the back seat - making sure the body of the sensor isn't near any metal. Then turn the Jeep on and see if the light stays off, which would point to a bad sensor.

    I should say I have no idea if there's any "memory" involved here, something that might be need to be re-set by discoing the battery - maybe someone can answer that? Couldn't hurt to try it between sensor swaps though.


    Other than that I'd say you'd probably have to pay someone to hook it up to a scanner.

    I know a lot of the auto parts chains do free CEL scans, but I don't think they do ABS scans for free
    It does come on right at startup. And stays on. System did go dry but issue was before the new parts. New sensors are all verified good and fuses are in working order also. Jeep has been without a battery for 3+ years so pcm reset is not the issue.
    There may well be air in the ABS pump but I have no way to cycle the pump. I know nobody with a scanner and the jeep isn't registered to get it to a garage.
    If there is a way to manually power the ABS pump via "hotwiring it" to a 12volt source I would do it but I don't know what wires to energize.
    White 98 limited 5.9 (NOT A 5.9 LIMITED) Magnaflow cat and cat back, Edelbrock ceramic coated headers, Edelbrock aluminum heads, Meziere electric water pump, Spal HP 16" E-Fan, Spal fan controller, Comp cam 20-746-9, mopar 1.7 roller rockers, custom set of timing gears, steel under drive pulley for the crank, single plane mpi intake, Holley 52mm TB, accel cap, rotor, and coil, Taylor 10.5 wires, SCT tune, 180 thermostat, Spectre twin 4" cold air kit, and enough 1/0 gauge cable under the hood to run a small factory!

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    Forum CONDUCTOR Man Z88Z's Avatar
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    I'm in the same boat on this BTW.

    It's something I have to look into, although I might pay for a scan before I dig into it. I figure as long as the ABS system is along for the ride I might as well have it working, lol.



    PCM reset wouldn't help in any event - I meant something more along the lines of........

    If it was on because of a bad sensor and you replaced that sensor would it cancel the ABS light the next time you turned it on, or is there any kind of memory in the ABS brain that would require a battery reset? I'm guessing it should cancel the light but I don't know that for a fact. (the brain is the little black box attached underneath the ABS block on later ZJs. On early ZJs it's a separate box on the left inner fender)


    I was thinking about the hot wiring thing, but I'm thinking that could be difficult. Getting power to the pump to cycle it probably wouldn't be that hard, but I don't know if that would do much by itself.
    I figure you'd also have to find a way to activate the valving inside to clear each passage, maybe even in a certain sequence - and I don't think you can necessarily do that through the external wiring at the connector or whatever. I believe that stuff is mostly sensor inputs and the brain decides when to open or close valves. I'm guessing the scanners duplicate those inputs and fool the valves into activating.

    It's an interesting setup.
    The brain has plastic rods that reach up into the block to activate the valves. I was wondering if you could separate the brain from the block and manually work the valves, but you'd probably still have to know the sequence, maybe? I haven't looked into it but I'm (totally) guessing the FSM doesn't have the diagrams for stuff like that, not to mention it's underneath the block and might not be that easy to access. I'd be a little concerned about the pressures involved and whether a valve or something could travel too far or blow a seal without the rods in place - but that's not too likely as the brain doesn't seem to be reinforced to stand up to that kind of pressure.


    I've seen people mention bleeding the brakes after getting the ABS to cycle by doing hard braking on gravel or slick surfaces etc. - but that needs the ABS to be working in the first place. (I'm pretty sure once the ABS system detects a problem and the light is on the system has deactivated itself and does nothing)

    Of all the stuff I've seen covered on the forums, ABS problems don't seem to get a lot of attention

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    Member rtaylor231's Avatar
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    Quote Originally Posted by Z88Z View Post
    I'm in the same boat on this BTW.

    It's something I have to look into, although I might pay for a scan before I dig into it. I figure as long as the ABS system is along for the ride I might as well have it working, lol.



    PCM reset wouldn't help in any event - I meant something more along the lines of........

    If it was on because of a bad sensor and you replaced that sensor would it cancel the ABS light the next time you turned it on, or is there any kind of memory in the ABS brain that would require a battery reset? I'm guessing it should cancel the light but I don't know that for a fact. (the brain is the little black box attached underneath the ABS block on later ZJs. On early ZJs it's a separate box on the left inner fender)


    I was thinking about the hot wiring thing, but I'm thinking that could be difficult. Getting power to the pump to cycle it probably wouldn't be that hard, but I don't know if that would do much by itself.
    I figure you'd also have to find a way to activate the valving inside to clear each passage, maybe even in a certain sequence - and I don't think you can necessarily do that through the external wiring at the connector or whatever. I believe that stuff is mostly sensor inputs and the brain decides when to open or close valves. I'm guessing the scanners duplicate those inputs and fool the valves into activating.

    It's an interesting setup.
    The brain has plastic rods that reach up into the block to activate the valves. I was wondering if you could separate the brain from the block and manually work the valves, but you'd probably still have to know the sequence, maybe? I haven't looked into it but I'm (totally) guessing the FSM doesn't have the diagrams for stuff like that, not to mention it's underneath the block and might not be that easy to access. I'd be a little concerned about the pressures involved and whether a valve or something could travel too far or blow a seal without the rods in place - but that's not too likely as the brain doesn't seem to be reinforced to stand up to that kind of pressure.


    I've seen people mention bleeding the brakes after getting the ABS to cycle by doing hard braking on gravel or slick surfaces etc. - but that needs the ABS to be working in the first place. (I'm pretty sure once the ABS system detects a problem and the light is on the system has deactivated itself and does nothing)

    Of all the stuff I've seen covered on the forums, ABS problems don't seem to get a lot of attention
    Just read in the chiltons book that if no issues are detected in 50+ run cycles the ABS light will reset itself, or a scan tool is required. Only catch is how long do the run cycles need to be!? Also that it doesn't matter how long you have the battery disconnected for, if it sees an issue is saves it till its dealt with!
    Last edited by rtaylor231; 06-16-2015 at 08:51 AM.
    White 98 limited 5.9 (NOT A 5.9 LIMITED) Magnaflow cat and cat back, Edelbrock ceramic coated headers, Edelbrock aluminum heads, Meziere electric water pump, Spal HP 16" E-Fan, Spal fan controller, Comp cam 20-746-9, mopar 1.7 roller rockers, custom set of timing gears, steel under drive pulley for the crank, single plane mpi intake, Holley 52mm TB, accel cap, rotor, and coil, Taylor 10.5 wires, SCT tune, 180 thermostat, Spectre twin 4" cold air kit, and enough 1/0 gauge cable under the hood to run a small factory!

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    Junior Member Red Rocker79's Avatar
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    I would assume that this ABS is no different than most others; since the sensors are good, and are confirmed working, the pump might need to be cycled to induce the system back into working condition. Although I've never personally had to do this after I've done brake work before. Though I don't usually get cars coming in with bad WSS's to my shop.

    If it were my own truck, I would hook up a scanner and run a quick diag. to confirm there are no other issues present in the system, or perhaps something that's causing it to go offline.

    Even if it's the ABS light on, and not the CEL, you'd still get a readout of what's causing this issue, and at least a trouble code to further source. That's one good feature of OBDII.
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    Member rtaylor231's Avatar
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    ABS fault is still active, never bothered to deal with it other than pull the bulb. I don't have access to a scanner that reads ABS faults. The entire brake system minus the ABS pump assembly was removed and replaced so it was bone dry.

    - - - Updated - - -

    What I'm really looking for is a possible way to cycle the pump and soilnoids without a visit to the stealership.
    White 98 limited 5.9 (NOT A 5.9 LIMITED) Magnaflow cat and cat back, Edelbrock ceramic coated headers, Edelbrock aluminum heads, Meziere electric water pump, Spal HP 16" E-Fan, Spal fan controller, Comp cam 20-746-9, mopar 1.7 roller rockers, custom set of timing gears, steel under drive pulley for the crank, single plane mpi intake, Holley 52mm TB, accel cap, rotor, and coil, Taylor 10.5 wires, SCT tune, 180 thermostat, Spectre twin 4" cold air kit, and enough 1/0 gauge cable under the hood to run a small factory!

  12. #12
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    Without a scan tool that can talk to the ABS system, it's impossible to bleed the ABS.
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    Forum CONDUCTOR Man Z88Z's Avatar
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    Quote Originally Posted by rtaylor231 View Post
    ABS fault is still active, never bothered to deal with it other than pull the bulb. I don't have access to a scanner that reads ABS faults. The entire brake system minus the ABS pump assembly was removed and replaced so it was bone dry. ..
    .
    Quote Originally Posted by comptiger5000 View Post
    Without a scan tool that can talk to the ABS system, it's impossible to bleed the ABS.

    Rob, when you say impossible to bleed you mean cycling the ABS pump to bleed the block, yes? Or do you mean the whole system won't bleed correctly?

    Like rtaylor, my 93 brake system (all 98 ABS and brake parts on OBD2 wiring) was dry before I installed it. Drip bled it first and it seems like the brakes work well, although my ABS light is on.


    Any idea if the ABS will throw a code solely because it's not bled? I'm guessing no, and that it's sensing an electrical/sensor problem somewhere.

    I've read you can theoretically bleed the block by doing hard stops on gravel, sand, something that will activate the ABS - but I've never been too sure about that, like where would it displace the air to in an intact system?
    Plus, more importantly - that's not too much help as that relies on the system working electrically in the first place and I'm pretty sure anything that sets the ABS light also renders the whole system inactive, yes?

    And would I be right in assuming/guessing that shops with aftermarket high end scanners (like for example, the Snap-On etc. ones that can set fuel sync) can probably do the bleeding too?

    Last time I was at the parts store I noticed the "non-interactive/read only" scanners that can read ABS and OBD2 codes have come way down in price. Poopboys had one for under $90 that supposedly covered our ZJs, but I figure I'd research it a bit more and would most likely spend a bit more than that to get a better one if necessary.
    Won't help with the forced cycling/bleeding of the block but it would at least detect electrical problems, I guess, lol?

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    RallyJeep GO
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    I'm not sure if air in the ABS will cause it to fail the self test and throw the light. It wouldn't surprise me though. And yeah, if the ABS light is on, the ABS system is disabled.

    And yeah, I mean that you can't bleed the air out of the ABS pump itself without forcing it to cycle. I don't think the gravel road method really works very well. Air in the ABS pump could make the pedal a little spongy even if the rest of the system is bled perfectly, but I'm not sure how noticeable it would be.

    At this point, I'm 99% sure my ZJ will be getting an ABS delete in the near future. Mine has started flaking out and actuating randomly when coming to a stop (almost got me into an accident the first time it happened), so the fuses are pulled right now anyway. I've had far more times where the ZJ abs has annoyed me than times where it's been helpful, so I see no benefit to keeping it. I need to re-do the main rear brake line anyway, so I think I'm just going to re-plumb the lines in the engine bay and toss the ABS pump in the scrap bin. Pulls a few pounds off the nose (and up kinda high) too.
    1998 ZJ 5.9 Limited - Deep Slate
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    Member csouers's Avatar
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    Reseat the ABS Module connector. Could just be a bad connection at that junction.

    - - - Updated - - -

    Quote Originally Posted by comptiger5000 View Post
    Mine has started flaking out and actuating randomly when coming to a stop
    The tone wheels and sensors clean and aligned properly? I once had one of my rear sensors out of adjustment and it did exactly what you described. I didn't make it down the driveway before it acted up. A realignment fixed it. The fronts, as you probably know, are non-adjustable.

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    For mine, it's probably a wheel speed sensor. Fronts look fine, no crap in the tone rings. I need to do rear wheel bearings anyway, so that would be the time to take care of it if it's a rear. I just haven't decided if I really care to fix it or not.
    1998 ZJ 5.9 Limited - Deep Slate
    Mods: Big trans cooler, 231 swap, Indy MA-X heads prepped by IMM, Comp 20-744-9 cam, 1.7 HS roller rockers, 52mm TB, Airgap manifold, DT headers and full 3" exhaust, SCT tune homebrewed by me, Martin Saine valve body, B&M tranny pan, magic suspension made from unicorn tears, power steering cooler, lots of lighting mods

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