Ford Explorer Sport Trac: ABS Light On / WSS Signal I Can Not Explain??
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- Опубликовано: 6 фев 2025
- We some times get a seemingly simple diagnosis we can't explain. This is one of those times. This 2002 Ford Explorer Sport Trac came in with an ABS light on and a not functioning Right Front Speed Sensor. Simple right!? -Enjoy!
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Others have said it before me, but salt and moisture inside the sensor makes electrolyte, two electrodes by the open circuit pickup coil. Only a few mV though due to similar metals with differing levels of corrosion.
But, you also need to remember that the Pico is a high impedance device, 1Megohm, so you are in effect measuring an open circuit voltage. As well as generating those few mV, the chemical battery will be a low impedance compared to the Pico input, so that's why your AC voltage was roughly similar in that test.
The actual ABS module will have a lower impedance loading and I would be surprised if it didn't have a bit of bias voltage there to detect an open coil.
Backprobing with the Pico at the ABS module would tell a different story.
Keep up the great work Eric!
These points echo my previous comment and all seem plausible to me too.
Nice explanation pal.
yes, Salt water conducts electricity about as good as copper does too.
I am a DIYer who has typically had mostly older vehicles. Only ever had one car with ABS. My wife keeps wondering why I keep these older cars running. I have to say that it would hurt to have to replace an otherwise good wheel hub so that I could match it to a speed sensor. Yikes!! I wish I could get the wife to see this video. Maybe she wouldn't mind the older cars so much! Thanks MR O for another great vid!
Your work to edit this video has not gone unnoticed. It was outstanding. The information and troubleshooting process was explained perfectly too. I loved the valve stem cap tip, the "be patient or fast forward" and the "it should be an Allen fastener, or it's going to be" comments. I consider this one of your best videos.
Well thank you Wyatt , that means a lot to me. From the comments I am reading it seems as if my explanations were not good enough though as many people are asking questions that I thought were clearly answered in the video. Oh well, next time. But seriously, did you like the editing in this vid? I thought it may be a little easier for people to see the scope as opposed to shining the camera at it :)
The editing definitely stood out for me. It reminded me of how Paul does his videos. (The voice continues without a pause as we go to a visual of the scope). I don't know how to do that yet, but I think it really adds a seamless visual experience. I know it adds a lot of time to produce the video, but man, it's very professional. Ratches and Wrenches is good at this as well and you know how good his videos are. There's a new girl in town making a huge impact in the car world. In part because she's beautiful, but also because she has a great sense of humor, and kills it in the editing room. Sarah-n-tuned.
ruclips.net/channel/UCHSbIfwVuec_BwUrYAqN_qw
The further analysis of both front wheels is what makes SMA a step above every other shop. 98% of shops would just diagnose the one bad wheel, perform the repair and ship it. Not caring about come backs or customer complaints. I want a mechanic to give me the WHOLE story and explain to me all that is going wrong with my car. If I do not opt to fix those additional problems that's on me. But I still want to have someone intelligent enough to pick up on all problems big or small and report their findings to me. I might not understand all the electronic discussion in this video but I still love watching it so I can learn more about ABS systems on vehicles. Another top notch video!
The MAC tool guy loves you both, Eric O picks out the tools and Mrs. O' cuts the check for said tools. :)
Seconding all the accolades for video production. The way you did this allowed me to get immersed in the video which means more learning takes place.
I would not be a happy bunny when i found out the sensor was to long for the hub.
Great diagnosis. Great shirt Mrs O!
I was a ground equipment mechanic in the military and that equipment does not have ABS but my guess is part of the problem is the salt and water producing a voltage (maybe that isn't the correct way to say it). I also agree with the other people that it could be a ring problem too. Much good luck! Love your work!
"Every tool has a hammer side" I love that quote.
Great video Eric! I feel your pain with the salt. Northern Michigan here and everything is rusted! "Every took has a hammer side" BEST QUOTE EVER! Lol The valve stem cap is an excellent idea and I'll be stealing that! Thanks!
those are the inexplicable things of mechanics ... good video friend! waiting for the second part !!!!
Errors like that can make one develop brain worms. Very annoying. Very good video. Thx for sharing. ☺
The waveform looks good only the amplitude was to low.
Thats because the air gap underneath the sensor is to big.
After replacing the sensors the amplitude got better because you cleaned the surface of the hub and the sensors now sit lower.
On the left side this worked fine but on the right side the air gap is still to big.
Replacing the hub would fix your problem.
But as an experiment you could also grind a litle piece of the surface so the sensor sits lower in the hub. Would be cool to try to see if this works and it will only take a few minutes with a grinder😎
Maybe just leave the shim out and see if that helps?
However, the sensor should come alive and register at higher wheel speeds, which it did not. The air gap is not the main issue here! Looks like the sensor coil is almost open circuit :)
Pine Hollow Auto Diagnostics Mayebe it does come alive now, he has not driven the car and looked at the scandata after he cleaned the hubs.
I noticed you posted a new video looking forward to see it!
Salt causing galvanic response? Thanks for another great vid!
Hi Eric!!!!....Great video!!!!....fancy tools and clothing too!!! hahaha....uuummhhh....all Crusties(green white yellow) produces all kind of electric and electronic phenomena!!!...in order to make a repair to last good time, best is replace both hubs!!! more expensive but new parts work optimal. You could do ohm test in both sensors, cross jumper both sensors, turn the wheels in both directions too, and visual inspection the notched rings inside hubs if its possible, check for crusties in the cables and conectors!!!...The sensor itself is not a separate stage of electronics, in fact the sensor is an internal part of a electronic circuitry!!!...it is located outside, but in terms of a electronic component could be visualized inside the ECM!!!...the information and signal procesing depends on how the sensor is conected inside the ECM. Could be one lead to ground, that eliminates the zero crosing!!!...could be conected to a filter circuitry!!!...or to a complex floating zero crossing detection, that is more complicated and fancy circuitry!!!...anyway, I think the problem itself is corrosion inside the hub (neglecting the sensors conditions first) and if it where possible to clean inside the hub it will change the shape of the notched ring, and thus producing a weird signal too!!!! Amplitude of signal is related to sensors distance, and frequency is related to speed and shape!!!....detection is related to filtering and signal processing!!! Thank you for sharing your toughts with us, and thake us with you in your videos!!!!....that is why I am a SMA fan!!!!! It is always fantastic see your work and learning diferent things with you!!!!.....Greetings to all at SMA!!!
Can't wait for part 2. I love your video's. Nice to see a down to earth tech. I sometimes have to do the same thing, stop and think.
That doesn't look like a sine wave to me looks more like a sawtooth wave but I'm probably going to get a comment explosion saying I'm wrong but brilliant editing and explanation of steps and troubleshooting keep up the excellent work, stay safe and well
you know a massive amount about electrical systems, i have been learning lots, thanks for the brake cleaner and extractor set easy out demo, and Mrs. O is wearing a well designed shirt
Good information on Pico... and excellent video editing.... Also statement of the video "Every tool has a hammer side" totally agree..
The salt on the door looks like a painting of trees and snow on the ground. Eric O. needs a giant 'fro and a paint brush. Happy trees.
Panhead49EL I can see him doing that. He doesn't quite have that soothing voice though.
ever sen eric and bob ross in the same place at the same time lol
I'll have to find a picture of Bob Ross and Photoshop a Jeep hat on him!
needs a pet squirrel in his pocket
parts consistency makes this job a real pain.
too bad you don't have a bunch of old shims, stack them up until the new sensor clears. i know, hokey repair but it would probably work.
anyway, another great video, thanks Eric.
Thank you for the video sir. I was totally unaware of being able to download pico's software to play with. That is awesome.
Try before you buy!
Ya know watching you try to get that bolt out made me smile....the whole things is what i go through all the time...except the end....it never ends that fast for me...never...something like that for me would involve 3 hours welders and torches drill bits and taps....
Great work Eric, appreciate you taking the time to record.
I would love a SMA sweatshirt like Mrs. O's. Only mine should say "we the people". Great video as always.
Much excitement on the west coast Canada today! 3/8 cordless Mac ratchet with Dewalt batteries arrived at the door.First seen on S.M.A. vid. And a bonus mac tool truck to stick on the fridge!!!
Signature sweatshirts ??? Hoodies ?? Just what we need here in Anaheim. 79 degrees here today BRRRRRRRR.
Ah, just wait a week or two, the fire will warm you up.
Excellent job thank you for the information and your presentation you've came a long way!
NICE PNP view, just like Scanner. It was cool. You're just lacking 3 things- more light, a lovely Assistant, and more cowbell.
Ivan has nailed it. But the near open circuit might be in the leads, or connector.
Nice tip about using a valve stem cap to keep the dirt out of the sensor holes when cleaning the mounting surface of the hub. Wow, The OE wheel sensors usually cost more than an entire aftermarket hub with the sensor. Often the brake rotors are so rust seized on the hub and inboard sides pretty rust ravaged too that it might be wise to change the pads and rotors now than deal with brake pulsation. I would ascertain rotor condition and likely try to sell 2 complete assemblies and let them know the signal is weak on the left side too and if that sensor can't be removed without damage or signal strength improved by cleaning the left side hub sensor mounting surface, I'll have to replace both hub assemblies.
Exactly why I never wanted to be an engineer, I learned their were tolerances and values that I would never understand.
Good example of raw data versus processed data.
"Look at all my trials and tribulations,
Sinking in a gentle pool of antifreeze.
Don't disturb me now, I can see the answers...."
[The ballad of Eric O.]
I feel you want to test those sensors, you need to load them down with the right load resistance. Your scope has many megohms of input resistance. The bad sensor might have many kilohms of extra series resistance but that won't show on the scope with its high input impedance. Also a coil can't put out D.C., there is likely a little battery consisting of a break in the wire, some moisture, and a different metal, like the solder or the internal lug.
Another good video Eric O. Good little trick with the valve cap thanks eric o.
I have a suburban that had about 750-900 milivolts on three wheels and one that put out about 300 mv and it was tripping my stabilitrac during acceleration I used a caliper and the air gap in the hub was within spec. I tried closing it up a smidge and Also tried a different abs sensor in the hub and still same result. So replaced the hub and it worked putting out the Correct voltage.
im so glad we don't have to deal with rust and salt down here in phx
its phx so smogs about normal
The air cap trick to plug the hole was Cool👍🏻👍🏻👍🏻👍🏻👍🏻 Thanks I’ll reminder that one.
Very interesting diag, Eric! Did you happen to measure the resistance of the two sensors by any chance? And I've run into the sensor being too long for the hub before too. Maybe just stack some shims or thin washers to set the proper airgap?
or an o-ring around it, depending on the design.
Instablaster
Hmm, I got nothing for you on this one. Looking forward to the final diagnosis. Thanks!
Nice editing with computer screen captures! I have no idea what the ABS module can't understand. I am baffled too...
I agree it would be beneficial to see the signal when connected. After going over the video, Eric was getting the dc component when not connected to the abs so the dc component has to be generated by the sensor. Maybe the noise is being rectified by the sensor causing the dc and that is blinding the abs from seeing the ac signal.
There's so much salt under that car I mistook it for a bag of McDonalds french fries.
The front hub assemblies comes with a ABS sensor installed. You can actually get a front hub with a ABS sensor cheaper than the OEM ABS sensor by itself.
You can only get a front hub with sensor cheaper if you get a generic Chinesium hub that's probably going to be a callback when it fails prematurely. If you want to go that cheap route, at least compare apples to apples which would be the price of a generic sensor alone, not the OEM sensor price.
Considering the work to do a hub, a generic hub is the worse economy possible. That does not mean you have to get an OEM hub either, just a major brand which (almost) always costs more than the sensor alone.
Really good production and editing in this one.
Remember what Ivan just went through in S.I. with "leaking noise"? All that chloride acts like an antenna for outside RF. It looks as if there's a weak leak to ground. Electricity flows FROM negative TO positive. There is so much RF leaking- it's interfering with the signal. Ohms the both leads of the WSS plug, EBCM side- to body, knuckle, etc. (ground) and check for a closed circuit. Just my theory.
I'm stumped, that's for sure. I do hope you find a solution, Eric. Also, the bottom of that vehicle looks like it ran over a sack of flour. Hate that stuff. I know it all too well living here in Ct.
Always love new tools and great video Eric as always.
Holy moley... seeing all the salt under that thing does not leave me wondering anymore on why your cars are almost rotted out after one winter. :O
Probably more than one Winter's worth of salt. They don.t seem to go near a car wash over there!
I have the "Waekon 20560 ABS Sensor Pinpoint Tester" where it sends a signal through the wire harness to check wiring integrity to the abs module. Works great, you can watch it on the scan tool!
Thinking that salt and water (an electrolyte solution) have infiltrated into the open wheel speed sensor, creating a battery between the open connections (possibly 2 dissimilar metals like copper and solder). That would explain the small DC offset on the open sensor. Did you try comparing the resistance of the 2 sensors?
Was the wiring from the sensor to the connector on the right wheel good? No signal at all = possible broken wire?
The speed sensor has to be made by the same manufacturer or they just have to be the same length? It sounds like you have to get hubs and speed sensors as matched pairs or by the same manufacturer.
Best video yet up close with the Pico screen really helps, and of course, every tool has a hammer side. Wish you sold SMA hoodies
RollingRock/fan I would buy two of them
Me too
Me too signed also
Me too..
Which side of the pico is the hammer side? :)
Nice video, I just had a Dodge Dakota with a dead aftermarket sensor/hub on it. Ohm'd out ok and had a voltage reading on the scope when spinning the tire, it also has a static volt reading even after removing the hub/sensor assembly from the truck??????
It has to be some kind of galvanic action from all salt brine on the roads the last couple weeks..............
I noticed that after the repair the red trace seamed to be still starting at an offset? I am not proficient with the scope (working on it) but that is what I saw. Also, I had a similar issue with an 07 Edge AWD. My issue was the customer had driven it for so long with bad WSS's that it caused the ABS module to go all caddy wampus and was going into a no comm. state. This issue had no rhyme or reason and was very sporadic making it a bear to diag. Ended up replacing 2 WSS's and the ABS module. Looking forward to the next vid.
My brother in law, who is a retired Marine, would flip out watching you hammer with anything other than a hammer. He's really strange about who and how his tools are used. We all have our little quirks.
Hi Eric & Mrs O
Great video makes a person think and provides a useful tip for others Valve cap and install extraction tool as well. I have one question, what side has the longer electrical run to the ABS control module? As you showed the hall sensor is only lower amplitude not completely dead. If you measure line resistance between L & R side I expect you will find a minor difference on the side with the longer run length. That in conjunction with a sensor that has possible leakage due the salt & corrosion issues has brought the signal performance to just below operational threshold levels. Or as with all electronics THERE IS A BUG in the system!!
Interesting how the signal is pushing slitley above the 0v scale 🤔 did the sensor go high resistance 🤔 Eric O @SouthMainAutoRepairLLC
I wonder what what happen if you put a small value pull down resistor on that wheel speed sensor to bring it down to 0V if that would allow the abs module to read it. I know thats not a fix by any means but it would show you how small the tolerances are for what it will and will not read. Great videos look forward to watching them.
Do you have a function generator on the pico scope or elsewhere? If so, you figure out exactly what amplitude the computer needs to see and whether or not the offset is a problem. You could leave it at zero offset, and turn up the amplitude until it reads a signal, and then adjust the offset to see whether that has an effect or not.
I wish I did :( Actually the Launch Pad II that I use has that option but I do not have the devise to go with it. We know what the amplitude is simply by looking at the left side. We can also see that we achieved that on the right side. It would be cool to play around with the signal generator though just to see if an offset does or does not affect it.
You could always use the utest leads and run the left front sensor to the right front connector to verify the vehicle wiring and module. And/or do a little swapnostics with the sensors
Ha. Nevermind, I see you did that. I replied before I got that far into the video
In the tsb for gm trucks with unwanted abs stops it says that the wheel speed sensor has to be able to produce more than 350mv @ 1rev/second of the wheel. I think that the abs module on the explorer doesn't see any wheel speed because the amplitude of the waveform isn't high enough to trigger the analog to digital converter in the abs module.
Great video as always thanks brother injoy your videos. Keep up the great work see you in the next video. I think sometimes you over think stuff and you confuse your self because of the great mind you have. Keep up the great work you have this in the bag your the best
I'm not a real elec-chicken and I don't play one on Broadway, but I suspect the ABS module is watching for the sine wave crossing zero volts. Each time it crosses, that's a data point, and the time interval between data points tells the module how fast the wheel is turning. With a DC voltage raising that sine wave away from zero, what should be an AC signal becomes a DC signal that the ABS module doesn't recognize until its amplitude increases and its peaks push down past zero again.
As others have said, but I'd predict that the corrosion has just reached the point where a connection has corroded just to the point of stopping conduction. When you spin the wheel the signal is just strong enough to conduct across the gap through the salt but at a lower amplitude because of the resistance of the corroded spot. One way to test would be to either measure resistance which I predict is high, or, send a few volts down the sensor leads and likely burn the open section to fully open.
Just a thought but dissimilar metals in an electrolyte generate a voltage
That's what I think also
wak wak waaak
An unintentional diode junction acting as a detector.
I would think its all the salt generating voltage to a bad wire
Salt+water = electrolyte. Still need the two poles to generate a current = two different metals.
had that problem on my 01 sport trac (your one explanation)
no abs light on but abs kicking in coming to a stop.
Had to make a habit of starting to brake like 10 feet++ prior to where I normally would.
or else I would rear end someone or go into the intersection
I glance through the comments Eric and salt comes up a lot , and I think how your equipment gets coated like the floor , the lifts anchor bolts etc, this time of year a high percentage at the end of the day is cleaning up . You must have a good sealer on that floor , just saying , nice vid as usual .
It would be interesting to know if there is a difference in the resistance between the bad sensor and a new, or working, one. If there happened to corrosion in pigtail, would that resistance reduce the voltage seen?
Also, perhaps the ABS module has a voltage threshold before it reads the sensor (voltage and frequency) for speed to inhibit noise causing the ABS to engage?
And that's just it. The ABS is just barely at the threshold for code setting criteria on the l/f. Nice catch, for future issue. As for the bias voltage on the r/f, I'm curious if there was a resistance issue left vs right, even though they are both Moog bearings with whatever sensors they use. I have run into that on some aftermarket Chevy applications, where a customer has installed a new assembly on 1 side, ( due to a bad bearing not an ABS issue) and had an OE on the other. The OE had a lower resistance than the aftermarket sensor, thus had a higher MV signal than the new bearing assembly did, and the difference drove the module nuts. My thought is, if you ohmed out a new Ford sensor vs both the left and right Moog sensors, would they be the same, or ALL different? Anyways, you did fix the left side for now.. LOL
Water salt and different metals makes a battery.
Wonder why the mysterious voltage unexpectedly disappeared, and then showed up again another day...
I see the comments about two metals and such, are they talking about the shim and hub?
It's all Greek to me. Thanks for the video.
Eric, the scoop on the far wall in your intro looks like an Easter Island face carving. Creepy!
Lol...every tool has a hammer side. So true.
The analog to digital converter in the ABS module sees only the positive component of the AC sing wave. If you have a big enough positive offset, the module will see this as the signal being always 1. like when a hall effect dosn't pull the signal all the way down to ground.
Where that DC comes from? that i don't know
Mrs O running the office and cleaning up.
Hello Erick I had the same problem with a Honda Civic check all with pico and omhs as well as the harness changed the hub bering for an (aftermarket that the customer brought as well as the sensor) and no change. my solution was to replace hub bering sensor front honda dealer.
Sometimes older Mook hubs get magnetized and stops the wss from reading accurately. I had the same issue and found that out by chance!
Could of tried removing the shim on the week side may have increased the wave. if there was still clearance.
I’ve run into 3 times in the past month and have no idea why the ABS module isn’t liking it? Sure it’s a little low but I thought it should eventually pick up. Interestingly all 3 bearing were the same manufacturer of low line bearing. Hopefully if u find the answer please share! It’s baffling me. (And I’m sure my boss would like a proper reason as to why it’s no good, other than “it’s junk” lol)
Okay great tip Eric O. on that wheel speed sensor fit due to length difference from a standard size.
Go figure Chinese parts.. Will we ever get back to good ole American parts?
I remember from the olden days in Electronics class that any coil of wire acts like an inductor and can hold electrical energy in a magnetic field. Maybe the sensor (which is just a coil of wire) broke in such a way that it is acting like an inductor of a different value and causing some kind of delayed transient response with the meter. An internal short in one sensor might cause the two sensors to have different different inductance / voltages and maybe that is somehow causing the issue with the meter. Like I said, it's been a long time since school but I would look in that direction.
There 's your problem Lady! Galvanic corrosion is an electrochemical process in which one metal corrodes preferentially to another when both metals are in electrical contact, in the presence of an electrolyte. This same galvanic reaction is exploited in primary batteries to generate an electrical voltage
Blaine Steen - fancy words for the fine wire (32 AWG) from the coil inside the sensor transitions to the heavier wire is broke !
Thanks as always for the great lesson. salt salt and more salt you have it bad my friend
If the cables going from the speed sensors to the abs module were disconnected at the abs module, then any dc bias source in the abs module would be eliminated. What screen capture software you using for the Pico video inserts? Quite well done.
"Don't be surprised if when you take yours out it breaks !" That is why I paid someone else to do it !
If that was my car, I would just file the end of the sensor to the correct length and place a dab of silicone dielectric grease on it (for good luck). It "should" have no effect on the sensor operation. Actually if the clearance to the "exciter ring" is smaller, you will have a higher voltage signal at low speeds.
If you have lighting that uses ballast sodium or florescent it can induce noise into the body of the truck.
See if the seemingly defective sensor has a high resistance ground ... corrosion/battery effect?
If you're chasing a 30mV DC "phantom voltage", can try connecting a ground wire to bolt holding sensor into arm and other end to battery ground, see if DC offset disappears from picoscope. If disappears, can try to see if ECM reads it correctly then. DC must be introduced somewhere, either from sensor body or from frayed wire. If you had perfect insulation then 30mV couldn't get into it in the first place, correct? So, I think you'll be then looking for a worn-through wire.
Multimeter resistance checks of the sensors to see if they are different?
Multimeter a.c reading when connected only to each sensor?
Across the abs wires, for high resistance on both?
I agree with the right front sensor needing replacement. What I don't get is why there are two rear sensors when you only get a single graph on the scan tool for the rear. I was expecting a single sensor mounted in the differential. I hope there will be a follow up to this video.
There is only one rear sensor on this
Have you tested the abs wiring at the module where the wires from that wheel terminate into the computer? See if you have voltage there?
My guess is broken wiring further down stream between sensor and computer
i like that osha approved lift lowering system
Education Lesson @23:04 - Venturi Effect - en.wikipedia.org/wiki/Venturi_effect
&
The Good Stuff, Fluid FIlm a @23:22 - Rattle Rattle
all in one video. Eric is too good to us.
What if you already replaced one brand new hub up front and the same abs issue is happening? Abs light had been on for a while, drivers speed sensor wire was cut for atleast 2 years, 2003 ford explorer sport trac xlt finally the bearings started to roar. Replaced drivers hub yesterday.
You should try a capacitor in series with the sensor to see if the dc component goes away and the signal is recognized. Maybe there is some rectifying going on in the sensor
I too wondered about rectification, but if that was the case then the DC offset would vary with amplitude of waveform (which in turn varies with rotation speed, as these sensors do). So that seemed less likely.
Good point didn’t think of that. The cap should still be able to filter the dc component. It would be interesting to see if the signal would be recognized
Complementary to that, it would be interesting to know if the ABS unit has a strategy to detect sensor wiring fault, such as applying a constant current through the wires and measuring the (DC) voltage. If so, that capacitor you want to attach would defeat that strategy, and cause a code and probably lack of detection of an otherwise good AC speed signal. So I come back (as I've commented elsewhere) to being most interested in seeing what the signals look like when the sensors are attached to the ABS unit and operating.
Oh boy, an Exploder!! Look at all the crusties on that thing!!
The reason I suspect the module is not able to read this is the circuit needs to raise 0.6v above and below zero volts to switch the transistors on and off. The DC voltage offset could prevent this from happening. Capacitors are used inside the module to ensure this toggles around the zero volt line. It's great how RUclips can be used like a video IATN.
(Dan Hucklebridge) on escapes, I have seen several toner rings on the front....crack, throwing off the signal...showing zero MPH. they are available separately, and not too hard to replace on the cv joint. might be the same...for explorer sport?