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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47 thoughts on “A look at gm digital abs wheel speed sensor”
  1. Avataaar/Circle Created with python_avatars vasia visilievic says:

    Great info!

  2. Avataaar/Circle Created with python_avatars AKM Cars says:

    is the 25$ sensor!? or is the 180 euro wheeberings ?!?! c0050

  3. Avataaar/Circle Created with python_avatars Richard Ashcroft says:

    Will be tackling that on my 2011 Chevy Cruze

  4. Avataaar/Circle Created with python_avatars Derek Wolfson says:

    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.

  5. Avataaar/Circle Created with python_avatars LE H says:

    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?

  6. Avataaar/Circle Created with python_avatars Lawrence Kennette says:

    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?

  7. Avataaar/Circle Created with python_avatars rjh245 says:


  8. Avataaar/Circle Created with python_avatars Mike Chiodetti says:

    Good Info, Great Video!

  9. Avataaar/Circle Created with python_avatars FrugalPrepper's Garage & Garden says:

    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.

  10. Avataaar/Circle Created with python_avatars Brent McLaren says:

    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.

    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.

    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.

  11. Avataaar/Circle Created with python_avatars 73 SUPERGLIDE says:

    97 park with C1232 C 1234 C 1235 what u think

  12. Avataaar/Circle Created with python_avatars Jim Zivny says:

    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

  13. Avataaar/Circle Created with python_avatars Frank Gonzalez says:

    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.

  14. Avataaar/Circle Created with python_avatars Sercan Savran says:

    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 ?

  15. Avataaar/Circle Created with python_avatars spelunkerd says:

    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.

  16. Avataaar/Circle Created with python_avatars tinkerwest says:

    Man whoever gives these videos thumbs down are !@#$%^&*()…
    Always a learning experience and pleasure to watch these videos…

  17. Avataaar/Circle Created with python_avatars Steve Gilbert says:

    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.

  18. Avataaar/Circle Created with python_avatars Lucy and Jumper says:

    You're funny Eric,hilarious when u said "when the rust gets to your car,"SHOWS OVER".. Funny stuff,good job.

  19. Avataaar/Circle Created with python_avatars Rick Duncan says:

    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?

  20. Avataaar/Circle Created with python_avatars RC Hobbyist Extreme says:

    Typical stupid idea,exposed to the elements,guarenteed to fail.

  21. Avataaar/Circle Created with python_avatars Stuart Wright says:

    Are we going to get a vid on the Jag?

  22. Avataaar/Circle Created with python_avatars farmboy30117 says:

    I hope we start to see a lot more parts being made in the USA 🙂

  23. Avataaar/Circle Created with python_avatars K says:

    i pray for you for it not to be a v12 hahaha

  24. Avataaar/Circle Created with python_avatars Billy R says:

    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 !

  25. Avataaar/Circle Created with python_avatars Turbotomass says:

    Kia/Hyundai during a fault the module will stop sending the 12 volts to the sensor.

  26. Avataaar/Circle Created with python_avatars LeGrande Verde says:

    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.

  27. Avataaar/Circle Created with python_avatars Jimmy S says:

    Got a FORD Focus with the same setup. I wonder why GM copied the Ford design.

    Question.why did GM use a bearing hub that can accept a CV axle? Does that kind of bearing hub fall apart if there is no axle nut holding that assembly together?

  28. Avataaar/Circle Created with python_avatars Jeremy Anthony says:

    dude what the hell's with the old jaguar ? what's wrong with that pos? i thought you didnt work on those.

  29. Avataaar/Circle Created with python_avatars Bad Drivers of North Texas says:

    What is it with GM and their brakes

  30. Avataaar/Circle Created with python_avatars 3457 CVD says:

    Eric, Once again good job. You gave me information I can use.

  31. Avataaar/Circle Created with python_avatars arciefan says:

    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 !

  32. Avataaar/Circle Created with python_avatars Phil H says:

    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

  33. Avataaar/Circle Created with python_avatars Ryan Colley says:

    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 🖒

  34. Avataaar/Circle Created with python_avatars Phil H says:

    schrodingers box just released a new video. more bitching and bashing. check it out when you get time dr o

  35. Avataaar/Circle Created with python_avatars Baxrok2 says:

    Curious design. Jeez. Thanks for explaining this one Eric!

  36. Avataaar/Circle Created with python_avatars Wrench life 604 says:

    good video with the waveform.

    most techs would probably just read the code then throw a sensor at it

  37. Avataaar/Circle Created with python_avatars Jerrod Lindquist says:

    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…

  38. Avataaar/Circle Created with python_avatars Jerrod Lindquist says:

    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.

  39. Avataaar/Circle Created with python_avatars throttle bottle says:

    coming soon, left rear wheel sensor error code and bearing change 🙂

  40. Avataaar/Circle Created with python_avatars Rod Palm says:

    You can probably see that drop out using an ohm meter as well. You know, for us computer diagnostic challenged people. 🙂

  41. Avataaar/Circle Created with python_avatars Edward Kubiak says:

    is that a v12 Jag?

  42. Avataaar/Circle Created with python_avatars Ron Hart says:

    I see you're finally working on a real car (Jag XJ) 🙂

  43. Avataaar/Circle Created with python_avatars Tom O'Connor says:

    Waveforms are sure way to go even when its obvious. Handy info to know.

  44. Avataaar/Circle Created with python_avatars Andrew W MacFadyen says:

    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.

  45. Avataaar/Circle Created with python_avatars Hayward's Automotive says:

    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

  46. Avataaar/Circle Created with python_avatars Chris Thackray says:

    Nice old British jag in background

  47. Avataaar/Circle Created with python_avatars Borkzilla says:

    No fancy tone rings in that Jag there at the end!

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