A Look At GM Digital ABS Wheel Speed Sensor
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- Опубліковано 11 жов 2024
- Come along with Eric O at the SMA shop as he has a look at this 2011 Buick LaCrosse that has an ABS Light on and DTC "C0050 0F
Right Rear Wheel Speed Sensor Circuit Signal Erratic" Circuit / System Description:
The wheel speeds are detected by active wheel speed sensors and encoder rings. The encoder ring consists of permanent magnets. Each wheel speed sensor receives a B+ signal from the electronic brake control module (EBCM). The wheel speed sensor produces changing current between 7-14 mA on the EBCM signal circuit. As the wheel spins, the EBCM uses the frequency of the square wave signal to calculate the actual wheel speed.
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Due to factors beyond the control of South Main Auto Repair, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. South Main Auto Repair assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. South Main Auto Repair recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of South Main Auto Repair, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not South Main Auto Repair.
As a younger tech, I grab the scope for diag work all the time. Whether it's truly fruitful or not I'm storing data. Boss always asks why I'm "wasting time?". Thanks for going the extra mile and sharing your experiences.
not wasting time at all, you need to know what good looks like so you know what bad looks like when you see it!
I'm from Nova Scotia and a truck mechanic. Love your channel and really like watching you do your diagnostics. It's amazing and frustrating how electronics have taken over the auto industry and how little the public know about it. Keep it up. You are teaching us all. Haha.
I had a lovely french Peugeot the other day that was dropping out a front sensor. Turned out a stone had wedged itself into the magnetic ring. Good work Eric
Lovely and Peugeot don't sit well together.
Andrew W MacFadyen I know I like to think of myself as a bit of a comedian 😂😂
That PICO is an impressive piece of equipment. Nice comparison and great information about what voltage there using. Good morning Eric!
Love your videos Eric, I feel for you dealing with rusty rubbish, its that dry out my way that not much rusts until its 25 years old unless its been underground but thats a story for another time. Keep up the good work.
Good stuff, Eric! Gotta love the salt! Would be curious how those voltages change with the sensor unplugged, just to see what an "open circuit" problem would look like on the scope.
Funny story: last year I diaged a 2001 Lexus RX300 with unwanted ABS activation, no codes stored. Scan data showed that Left Rear wheel speed was erratic. Well I scoped the actual signal and spun the wheel. Textbook VRS signal...no issues. So I fired the parts cannon and replaced the speed sensor. NO CHANGE!!! So then I scoped the RIGHT rear wheel and sure enough a dropout was evident...classic cracked tone ring! I replaced the tone ring ($20), problem solved. Had to eat the cost of the speed sensor ($150) since that was the wrong call.
Moral of the story: never trust your scan data 100%! In this case I was using the Autel DS708 and apparently the programmers forgot what is left and right haha! Fronts were backwards too btw. Dang Autel.
Done scads of them here in Iowa rust belt as well, it was tricky the first time I delt with them, the voltage supply and was used to ohming the sensor back in the day
Nice video and analysis! Man the rust makes it harder to work on but it also brings in a lot of work. That bearing would last forever down here. Nice Pico waveform...mine will be here next Wednesday and watching as many training videos as I can until I find myself passed out drooling at wee hours of the morning :O
Curious design. Jeez. Thanks for explaining this one Eric!
Thanks for taking the time to educate us
I'd like to thank the brilliant engineers who had the wonderful idea of putting the wheel speed sensor inside the hub assembly. Because of their brilliant thinking, I now have to change a perfectly good $160 wheel hub just to repair a bad $60 wheel speed sensor.
nice one Mr O always a pleasure watching you .you make it look very easy .👍👏
Good info to share with the car repair nerd world
Great demo, it would have been a tricky diagnosis without careful inspection, and the Pico clinched the deal. I've spent years hand-wringing over which labscope to get and I think I've decided on the Pico. I like the idea of a waveform library although it would have to be pretty extensive to be of general value.
Nice work Eric O keep them coming. Thank you. Cheers.
The magnetic sensor explained. This type has only two wires, with one side tied to +12V. Mysteriously, the signal voltage takes on two rather oddball-seeming values. Not zero to 12V, nor zero to 5V, nor even zero volts to anything. So this is almost certainly a sensor which communicates by sending one of two different output _currents_. The receiving control module contains a resistor to ground, and reads the voltage that results from that signal current passing through that resistor. This mode of communication is known as a "current loop" configuration... current flows from the receiving device along the "12V" wire to the sensor, and then back along the sense wire to the receiver. The sensor sends information by regulating the amount of current. The current loop arrangement has two benefits: 1. Interference from electric or magnetic noise affects both wires equally, with an overall effect that cancels out. So less signal degradation from interference. 2. Makes it easier to design a system that has electronics in the sensor, yet uses just two wires.
Almost certainly, this module contains uses a chip like the TLE4923, data sheet here: media.digikey.com/pdf/Data%20Sheets/Infineon%20PDFs/TLE4923.pdf. See page 17 for the likely connection arrangement. Table 4 on page 11 (IS) shows that the low current is 4.1mA (+/- about 1) and the high current is 10.5mA (+/- about 2.5). And minimum ratio between low and high of x2. (These current signals are in the range of the "4-to-20mA" signal convention commonly used in industry.)
Looking at Eric's scope at 3:36 of the video, the resulting voltages at low and high are about 0.85V and 1.7V (ratio of about 2). So that corresponds to a receiving resistor (RS) of 180 ohms like in the datasheet, with the sensor producing (permitting to flow) 4.7mA and 9.5mA, which is in the range shown in table 4 for IS.
The sensor's block diagram appears on page 7. The "output signal" of the device is the amount of current flowing from the pin 1 terminal to pin 2. In this ABS application the VS terminal pin 1 is connected to +12V, and the output is the amount of current (4.7mA or 9.5mA) that the chip allows to flow through from pin 1 to pin 2. Don't be misled by the label of "Ground" on pin 1. In this ABS application it's the output wire.
Control of (most of) the current is performed by the variable current source element, shown on the block diagram toward the right as a circle with arrow. In this application the word "source" might mislead -- it just controls the amount of current allowed to flow, ultimately from the VS +12V terminal through to the "ground" terminal, which, as I mentioned, is used here as the output signal.
The block diagram also shows apparently two raw hall sensor devices, whose outputs are amplified. The "Schmitt trigger" is a device to compare those two values, and make an on/off decision. The "Schmitt"-ness means that the comparison is done with some amount of hysteresis, to avoid oscillations that might result if the mag wheel is at some intermediate position where the hall sensors read approximately equal readings. More explanation in the blurb on page 8.
The data sheet also tells that the TLE4923 has its own built-in regulator for internal use, and can operate properly down to 4.5V across pins 1 and 2 of the chip (and up to 18V). Adding that to the voltage the current will cause at the "output" (pin 2), that means the positive side can be any voltage from about 6.5V to 18V, and the chip will still produce the same two currents, and thus the same two voltage levels at the receiver.
AWESOMELY AWESOME show thanks again for doing what you do for all of us 🍻cheers Hunter O.
Eric, is the sensor still producing a AC signal and the sensor itself has a analog to digital converter built into it's internal circuitry that in turn outputs a digital signal or does it operate like a magnetic reed switch where if there is no magnetic field present because the tone ring is interrupting it and the switch ( sensor ) is put into a open or closed state producing a digital output/signal ? Glad to see your having fun with that Pico, you should have that fired up from the moment you walk into your shop to the minute you leave for the night ! If used right, it can give you real good direction right from the start of the majority of your diagnostic procedures ! The more you use it the more proficient you will get at it ! God Bless !
you know that is a fantastic question I do not know the answer too. HOWEVER, when that car or one like it comes in for service I will have an answer for you. I ASSUME it operates like a magnetic reed switch where if there is no magnetic field present because the tone ring is interrupting it and the switch ( sensor ) is put into a open or closed state producing a digital output/signal. Easiest thing to do will be to test it :) . I will let you know, again that is a fantastic question!
I believe it is a two wire sensor, so I would have to agree with ya that signal return is being brought down from 2v to 1v by some type of circuitry that operates similar to a reed switch built into the sensor ? The 12v supply I would think is to power up the sensor itself !
See the comment I posted 2017-02-02 for info on the sensor, signals, voltages etc.
You keep taking the time to put out these excellent videos and I will certainly say thank you as I know this is not an easy process as it slows u down some . Great job !
Thanks for showing me what I'm in for in a few years! :)
Automakers just can't leave well enough alone. Gotta keep changing everything. If I didn't know any better I'd say they're doing this on purpose to trip up DIY'ers ...
Yes and they make a ton of money through their parts department.
Waveforms are sure way to go even when its obvious. Handy info to know.
You look like its cold there. Nice Vid as usual. You must see a lot of ABS wheel speed problems
Bahhh warm here. In the mid 30's today!
NICE DR. O
AS ALWAYS
You're funny Eric,hilarious when u said "when the rust gets to your car,"SHOWS OVER".. Funny stuff,good job.
Eric, Once again good job. You gave me information I can use.
Hey south main, love your videos!
Knowing the condition of the roads in North America and the salts and chemicals used during the winter it almost is a planned failure. Good video
I hope we start to see a lot more parts being made in the USA :)
Trump says we will :D
Excellent! Another SMA vid to keep me occupied here in Sri Lanka on my holidays, another couple of vids a week please :-)
I see you're finally working on a real car (Jag XJ) :)
these a commonly known as magneto resistive wss, generaly are surplied with a voltage around 11-12v then the signal return will match the power surply until the wheel is spun and the window is blocked which causes the voltage to drop down... but not much at all giving u a hall effect type square wave.... generally used more often in newer cars now as they are considered more reliable and accurate at lower speeds, fairly easy system to diagnose. good video eric 🖒
they are also always only a 2 wire connector, easy to confuse with VRS type until u check voltages at the sensor itself
I don't believe these are magneto resistive. See the message I posted 2017-02-02 for details.
No fancy tone rings in that Jag there at the end!
Thanks for the video, working through this with my 2011 Lacrosse. I don't have a scope or a fancy scan tool so I am hoping to find something in a visual inspection (so far the front looks fine). Can these sensors be tested with an ohm meter?
And I noticed the ol' Jag in the shop at the end. I had one of those. Let me guess: Electrical problem or valve train...
Will be tackling that on my 2011 Chevy Cruze
Did you know that Timken is the supplier for GM wheel bearings? I know that GM has reduced their prices on wheel bearings to be competitive in selling them. The plus side with a GM bearing is the warranty!
Yeah they give a 12month 12,000 mile warranty. All the aftermarkets we put on are 3year...
Genericall, that is called a Hall Effect sensor. A digital "scope on a rope" from B+ to signal return would likely have show the gap. There are many variation of Hall sensors.
A more common configuration is the old Ford Profile Ignition Pickup (PIP) sensor. A metal shutter interrupting the magnetic force that switches a transistor.
Sadly, I'll bet you will be changing a lot of them as rust "jacks" that magnetic film of the bearing.
Remember it was switching at a low voltage 1 to 1.5v (ish) You'd been hard pressed to make that call with a digital test light. Besides I am sure it would have just pulled it to ground. Very low current circuit we are dealing with.
While turning the tire at a constant speed, you would observe the light stay OFF occasionally for a longer periods, instead of nice even blinks.
This type of sensor sends a digital signal by flipping between two different _current_ levels, that happen in this case to be about 4.5mA and about 10mA. Combined with a resistor in the receiving control module, the result is a voltage of about 0.85V and 1.7V. If you want the receiver to continue seeing a sensible signal during testing, whatever test method you use would need to show, or at least distinguish, those two voltages without diverting any substantial signal current. If you unplug the sensor, you can apply a voltage to the plus side (> 6.5V, say 12V) and measure the current to ground on the other side (use meter mA function)... this will alternate between 4.5mA and 10mA or so with wheel rotation. As an alternative, with the plus side of the sensor connected to +12V, connect the sensor negative side to the plus side of a bare LED , and the LED negative to ground. The two different current levels will cause two different brightnesses of the LED, and would allow eyeballing a rapid pulse pattern better than a meter would.
good video with the waveform.
most techs would probably just read the code then throw a sensor at it
Just found the same problem on my wife's 09 Acadia. Thought it was the wheel speed sensor at first, but I did find a diagnostic aid for how to test it. Good thing I only loaded the parts canon, and didn't light the fuse :)
I had purchased a new sensor (just in case), and confirmed that I could return it if not opened. Too bad it wasn't the sensor, that would have been cheaper :). When the sensor passed the testing, started looking elsewhere and found the damaged magnetic ring...
For anyone that this may help.
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Test procedure for WSS sensor on..
2008-2010 Buick Enclave
2007-2010 Cadillac Escalade, EXT, ESV
2009-2010 Cadillac XLR
2007-2010 Chevrolet Avalanches, Silverado 1500, Suburban 1500, Tahoe
2010 Chevrolet Camaro
2009-2010 Chevrolet Corvette, Traverse
2007-2010 GMC Acadia, Sierra 1500, Yukon, Yukon Denali, Yukon XL 1500, Yukon Denali XL
2007-2010 Saturn Outlook
To test for the "12 volt Wheel Speed Sensor Supply Voltage" from the EBCM with a WSS fault present, perform the following test:
A. Disconnect the Tech 2 and Key Off Ignition, Remove Key, Open and Close the drivers door to turn off RAP (Retained Accessory Power) and wait at least 60 seconds.
B. Disconnect the appropriate WSS harness connector.
C. Connect a Fluke 87 DVOM (J39200) across the wheel speed sensor "Supply Voltage" and "Signal" circuits from the EBCM.
D. Set the DVOM on DC volts, press the "range" button to the 40 or 60 volt scale and then press the Min/Max button.
E. Turn the ignition key on. There will be a quick momentary 12 volt pulse from the EBCM at key up. This 12 volt pulse is sent each time the EBCM is powered up after being asleep to check the WSS circuit integrity.
F. If the 12 volt pulse is present continue with the WSS component testing. If the 12 volt pulse is NOT present recheck the circuits between the EBCM and WSS before replacing the EBCM. Make sure there are no backed out or loose terminals at the EBCM, WSS, or any inline connectors using the appropriate Terminal Test Probe
Component Testing of the Wheel Speed Sensor
Note: This procedure is very polarity sensitive and if the WSS is connected in reverse polarity while performing the below procedure the WSS can be permanently damage. Please make sure the B+ is connected to the WSS Supply Voltage and the ground (Fluke 87 DVOM) to the WSS Low Signal Return. Use the appropriate SI wiring diagrams to determine the WSS Supply Voltage and WSS Low Signal Return.
A. Ignition OFF, disconnect the harness connector at the suspect wheel speed sensor.
B. Connect a 3A fused jumper wire between Battery B+ and the "12 volt High Wheel Speed Sensor Supply Voltage" terminal.
C. Connect a resistor of approximately 100 ohms in series with a Fluke 87 DVOM (J-39200) between the Battery Ground and the "Wheel Speed Sensor Low Signal Return" terminal. (Sources of a 100 ohm resistor: High Speed GM Lan terminating resistor, certain test lights, Radio Shack, etc.). Shown below is an example of how to properly connect your meter for testing.
D. Set the DVOM to the DC Milliamp scale.
E. The typical reading will be 4 to 8 mA for the "Low" reading and 11 to 16 mA for the "High" reading. As the wheel is turned very slow, a few degrees at a time, the signal will change from the low to the high reading as each reluctor tooth passes the WSS.
F. If not within the specified range, replace the wheel speed sensor.
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I was able to find a connector under the hood to access the circuit. - Handy as I have 12 volts handy there. I had already tested from this point back to the sensor connector, and validated no shorts or opens in the section of wiring I was looking at, so I cheated and didn't go find a 3A fuse. There was a 100 ohm resistor in the circuit anyways, so I felt safe without it. Even a dead short would have only resulted in 120mA.
Also confirmed that the silly thing does turn of the 12v source when it detects a WSS fault. Tried measuring voltage on both rear WSS sensor feeds, and got zipo.
BTW, thank you Eric for the great videos.
Are we going to be getting a video on that Jag?
Hey Mr. O: Were you turning the wheel in opposite directions (forward vs. reverse) in the first part of the video vs later (before and after the hub change)? I noticed the waveform was going in opposite directions. Just curious.
Did I understand it correct? When you turn the ignition on it has 12V, if the sensor is near the magnetic position and 0 V if it's at the non-magnetic position of the ABS-Ring ?
European cars started using that system almost 20 years ago, but usually BMW sheild the ferromagnetic ring in the bearing seal better from the elemets better than on that Chevy also BMW and Merc and LandRover normally protect the connectors by locating them inside the trunk or under the hood. Normally this style are more reliable than the old style toothed rings but wheel bearing wear can cause issues.
On Bosch system quick test is if the ABS light comes back on immediately the key is switched on it is a eletctrical fault, either sensor or wiring also if it fails the circuit integrity test the ABS module will shut off the 11.4 to 12v supplies to the sensor.
If the ABS light goes out normally then back on after 10 meters or so it is usually a wheel bearing issue.
Great video Eric...as usual. I have a 2005 Silverado V6 Work Truck. According to one of your other videos, my Driver Front Sensor is KAPUT...pump activates when stopping pulling the steering wheel to the right. I don't have the time or money right now to have it fixed .Can I pull that big ol' 60A ABS fuse temporarily? Thanks again for the videos.
I can't give advice on that. ua-cam.com/video/oXW0mqPrmPs/v-deo.html
On our 08 Chevy TrailBlazer we had to pull both the ABS and Traction Control fuses to make it safe to drive. I assume the steering wheel yaw sensor is bad (probably in addition to a bad wheel sensor or two). cdn.pximg.xyz/7488a1288e244bebe2c4cb7dd823956b.jpg
@8:06 Did The Equalizer drop his car in?
Was that a Jaguar in the background? Will it be on the next episode??
Good diagnostic amigo
Are we going to get a vid on the Jag?
I like the tractor trailer Tone rings better at least you just can replace the tone rings only.
Am I right that an "active" style ABS sensor will give a square wave and a "passive" style ABS sensor will give a AC Sine wave? Trying to understand this stuff for a custom swap.
Good job.....
Can this be done without an oscilloscope; with just a voltmeter?
I don't want to spring for a scope right now. Can I do a resistance test on a digital sensor? Can a standard multimeter read that high of resistance values?
Sounds like the factory repair manual is edited "off Shore" :)
This is GM, they are offshore...
South Main Auto Repair lol
Great info!
Good Info, Great Video!
also if you didn't have an idea of what the square wave is supposed to look like you can just go to the wheel on the other side but youd be really screwed if there were codes for both wheels
Nice old British jag in background
hi dear brother
my broplem in my car ford Taurus model 2006: there's a massege in dashboard screen telling me about ABS breack system(data error ) what's mean
it mean you have ABS breack system(data error ) . Check codes.
hey Eric man, so these digi sensors are still 2 wire like a traditional wss. any quick way to distinguish between the 2? I suppose just back probing one side of the harness when unplugged?
yeah but remember some VRS style float the AC on a bias voltage
South Main Auto Repair hmm good point, so did you approach this with the scope and fetch surprised by the digital signal or had you done the research before?
I looked at a diagram to see what kinda sensor it was. Still had no idea of what voltage range it ran on
South Main Auto Repair cool, thanks man, it's the one thing I wish I had better access to at the shop I work at, better resources for homework on systems I'm working on.. keep up the quality videos hombre!
@South Main Auto See the comment I posted 2017-02-02 for info on the sensor, voltages etc
coming soon, left rear wheel sensor error code and bearing change :)
lol more than likely!
Eric, if you needed to see what a known good was supposed to be, wouldn't you just go to the other wheel that's not throwing a code.
when I worked at a ind shop I put multiple ones in a week it seemed like haha you can look with a ohm meter to right?
Nope an ohm meter would show good readings in this case. Remember the sensor was good.
oh yeah but I shouldn't it show the resistance or whatever at the wheel
so the tone ring was just bad. that magnet strip. sucks they can't just replace that be way cheaper. but then business owners wouldn't make money I spose
is the 25$ sensor!? or is the 180 euro wheeberings ?!?! c0050
97 park with C1232 C 1234 C 1235 what u think
What is it with GM and their brakes
Thank you for this video, I hope it is same as my 2006, Cadillac DTS ! I keep my DTS off the road in Salt Weather . I see a great deal of your work, involves corrosion repair, of wheels.I know this " idea " , would cause revenue loss, BUT ! Because so meany of YOUR You Tuber's, are car nuts ! COULD you go over, what you think would keep , wheel corrosion " down " to a minimum ! I'm not a " fastidious NUT ", I just can't afford another $30,000 car, anytime soon.
Great
is that a v12 Jag?
I-6 4.2L
South Main Auto Repair Only half as good. Thanks dr o
You can probably see that drop out using an ohm meter as well. You know, for us computer diagnostic challenged people. :)
You might with a DVM but not a Ohm meter !
Kia/Hyundai during a fault the module will stop sending the 12 volts to the sensor.
really, hmmm will have to check this out. I wonder why
South Main Auto Repair yea the module kills the supply. maybe figures what's the point. or failsafe logic. you can make a special tool to read the sensor.
Is that a Jag in the other bay?
Yep... unfortunately
I love the V12s but I know how bad they can be to fix.
this one is a 4.2 I-6
I had one come here yesterday for upper ball joints. No idea what model or year - think it was an '04, but couldn't tell you the model. Guy couldn't wait, so he went elsewhere. Probably just as well ... LOL.
sexy closeup at 3:50 nice and sharp, crisp
dude what the hell's with the old jaguar ? what's wrong with that pos? i thought you didnt work on those.
LS swap? :)
alot of times traction control is affected and where your at that's not good nice video
You can sometmes tell which wheel is affected by which of the other sytems it takes down ---- speedometer stops working on the car types that I work on it is always the left right front, cruise control right front, sat nav input one or both rears.
احسنت
i pray for you for it not to be a v12 hahaha
Nice. Just like the Explorers always failed.
Electronic traction control... is it really necessary? All of this AI in cars just makes for dumber, less capable drivers. Back in my day, and no I'm not that old, you needed to know how to drive in bad weather, be aware of the interaction between your car, the engine, trans, your tires, and the road. It made you pay attention more. I guess like anything else, technology is great... when it works that is.
Electronic traction control is FREE once you have 4 wheel ABS. When the ABS senses one drive wheel spinning, it simply lightly applies the brake to that wheel shifting torque to the other wheel via the differential.
Not 100% correct. You do need to add an electronic pump that can activate individual brakes. Basic ABS doesn't need that; it only needs to be able to relieve pressure from individual brakes. But that's pretty cheap I guess.
4 independent wheel ABS has been standard for many years. Even before that it was typically 2 independent front ABS and then rear axle ABS. Ant additional cost was very small.
Gotcha
Typical stupid idea,exposed to the elements,guarenteed to fail.
Nice work Eric O keep them coming. Thank you. Cheers.
Thanks man!