Abs lite not workin

gmphil, Mar 14, 6:02am
hey all 94 vr commodore
mate had small nose to tail last week we replaced bumper in headlight so not a biggie . wof due this week and fail abs lite .
ive had cluster out bulb ok , under bonnet is fuse box the fuse is ok and 60amp in main box ok .
so where from here ? can abs unit be fixed or do just replace ?

tamarillo, Mar 14, 6:07am
if it was me I'd go somewhere that can plug in the diagnostic software tool.
It'll have a plug somewhere probably under dash.
Might have a fault code that can be cleared or at least tell you where problem is.

intrade, Mar 14, 7:41pm
94 possible pre obd2
the clue is you had a accident. you probabbly cut the abs signal wire you should really use a scope for this as a multimeter is not really good fast enough and its calculating a avarage as where a scope plots real time volts 1000 of mesurments a secound a multimeter makes 1 mesurment a secound and then uses the avarage of this mesurment to display on the screen.
You want to mesure the signal integrety of the all 4 abs sensors.
focus will be on the front for fault i would say but if 3 are the same the the one whom is not the same is the one with the fault most likely .
thats where it can get tricky because these mesurments are based on that the other 3 are ok and you dont know for sure.
also dont spread the pins of a connector .
Backprobing wiring is what to do and dont short the s wires with backprobing needles T pins is what you can use mesur with AC to see if you get a reading as the abs will be ac like signal.
let me know if you understand it so far?

intrade, Mar 14, 7:57pm
this is what i just told you without details multimter you need min max function so it records lowest and highest reading it did see if you dont have a scope
also be awear youtube is full of wrong information . this information is correct and its how most abs work. some have different designs and different voltage signals . like it seems older toyota use the full 12 volts on sensors as where never cars use 5volt rail voltage just like in the home pc same 5 volt rails . for supply to sensors
so could be anything but 2 volt will be minimum just like in this professional video

gmphil, Mar 14, 9:46pm
hey intrade to il have to go over wot u wrote carefully .
the accident was very minor as it broke a plastic bumper in headlight .
theres not wires there!
all abs units ive dealt with had light stayed on because a wheel sensor was crook .
this one dosent come on with key at all . was hopen bulb or maybe fuse but alas its not .
anybody nowhere the abs computer is located please save me pulling half dash apart

intrade, Mar 14, 10:19pm
So you carfully got over what i wrote ?
if you did? you would not now ask where the abs computer is
no where did i tell you to find the abs computer. ?

intrade, Mar 14, 10:35pm
find a correct wiring diagramm and post the immage on here.

gmphil, Mar 15, 9:13pm
morning intrade ! . ok when I read post three in four i was confused i have no formal training and don't have scope . so i thought best read re read make sure i understand wot u are saying no offence sum times i need to read snoopys post a few times too lol then decipher that as in back probing .wot is that ? ! so need to google or a like! . check u tube .
is full or stuff but all is about wheel speed sensors or pumps failing . i have NO light at all and didn't find anything relate to that except a piece on how abs works .stating that the speed sensor are read by ecu which inturn works the abs module to apply or not to apply each wheel .
bridged obd2 there are no fault codes stored !

intrade, Mar 15, 9:28pm
ok this makes it way more difficult for me to explain.
because i have a few years of training and i am still no expert but i know what is right and how to test correctly.
Burn this in to your brain its the most important thing to remember.
Do never ever assume anything assumption is the mother of all F*"*ups
Now mechanics want to go to the part to replace this is a bad way of doing things it works when the system is fully mechanical but its what has been breeding swapatrons. even manufacturer have endorsed this prctice for years and now it comes back to hount them as modules get sent in from new cars that are not faulty on brand new cars, all the swaptons have to now change there ways fast or be out of business its a world wide problem,
General motor now has made it compulsury for a scope to be used for diagnosing cars, they branded the pico-scope with there GM logo for dealer level tools.
This diagnostics that is required on new cars also can be used on older cars to not having to buy parts that are not broken.
i will make another post to see if i can explain what to do next since you said you got limmted know how.

intrade, Mar 15, 9:33pm
did you take it for a drive and hit the brakes hard with no one behind to see if the abs truely is not working if they lock up for more then 2 meters let the brake go as its not working and you need to have them not locked so you can steer the car.
i dont know how familiar you are with brake testing its why i write this that way.
That woud be the first thing i would do if you would bring the car to my shop

mechnificent, Mar 15, 9:45pm
Since there is no light on and you are sure the bulb is good, i'd suspect the abs unit is faulty, or there is no power getting to the unit, possibly a loose multi-pin plug, or there is a break/loose connector in a wire to the dash.

I'd look first around where you were working, and then near the abs unit. which you will have to locate somehow. Also. it may not be a power wire disconnected. it could be an earth. Did you disturb any earth points while working on the headlight or bumper ?

gmphil, Mar 15, 9:50pm
done small test in a congest cul-de -sak so no real speed but did feel like was pushing my foot off . car no wof in rego ! . u cant go shop around here with out passing the mr plod

gmphil, Mar 15, 9:58pm
no, no earth just it was just small 5 khr crash in just bend bumper bar in broke rite headlight so just pull bumper and unplugged headlight replaced both .

mechnificent, Mar 15, 10:13pm
The bump may have been enough to dislodge a poorly plugged in multipin connector. I'd try to find the abs unit. If there was a fault with the pump or control valves or sensors the light should come on. When the light doesn't come on, it means no power, or no earth, or a faulty control unit. Or a broken wire to the light.
If you have checked the fuse, and that power is getting through the fuse, then go to a holden forum and search or ask where the abs unit is located. locate the control unit, check if it has power getting to it, and that's it's earthed.

intrade, Mar 15, 10:27pm
if your abs works and no light turns on for test then it can only be the power to the bulb or the bulb is faulty or makes poor contact on the socket it resides in.
make abslut sure of that its not working.
i just need 10 meters to test a abs working here full throttle followd by full braking for 10 meters and you will hear brbrbrb woiiiiih noise from the abs pump.

gmphil, Mar 15, 10:30pm
ive discovered the control unit is under the front seat !
the owner is a very large guy . like the mega ten add size guy.
lol wonder if now with the crash motion he up out of seat in coming back down popped / damaged plug / wires .

gmphil, Mar 15, 10:41pm
not one hundred !. i pulled bulb from sim cluster held up to sun yup look ok in stuck in . so tomorrow will swap bulb from handbrake light with abs as there are all in little wedge holders this will eliminated bulb one hundred percent . and check that plug under seat
sorry real busy little street during day cars both sides cant get no speed .

mechnificent, Mar 15, 10:44pm
If you want to test the abs to see if they are working or not, the car will have to be etraveling over some certain speed for the abs to work. Some cars say twenty km an hour. so If you want to be sure you are testing the abs correctly, you need a lot further than the ten metres Intrade says. I'd use a dirt road or ven better if you can get it is a large bit of wet grass. Take it up quite a bit over twenty km/hr and jam the brakes on hard enough to start a skid. see if the pedal pumps and if the wheels lock and unlock themselves. If the speed gets below somewhere between twenty and twelve km/hr though the abs disconnects and stops working so watch out for that.

treachug, Mar 15, 11:15pm
Module under drivers seat is SRS (airbag) module. ABS module is found on inside right side 'A' pillar just below bonnet cable handle.

bigfatmat1, Apr 26, 8:14pm
I would first replace bulb in cluster visual cannot determine a blown bulb. If it's OK I while I had cluster out and plugged in I would check for to see if the common is positive or negative. Once switching is determined you can test at control unit to see whether you can activate warning light to eliminate wiring a test light is all you need. Abs system is pretty basic.

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