How To Test A Wheel Speed Sensor With A Scope - PicoScope Automotive
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- Опубликовано: 27 июл 2024
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We look at how to test a magneto resistive wheel speed sensor with the PicoScope oscilloscope. How will the signal look with this corroded BMW E90 sensor pick up ring when connected to the scope. This is a common issue on BMWs where the rusty reluctor ring causes ABS system faults; the stability control cuts in while driving normally!
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00:00 How to test an ABS wheel speed sensor with a scope
00:25 Rusty corroded wheel speed sensor pick up ring/reluctor ring
01:30 Break out lead to connect ABS sensor to scope for testing
01:56 How to connect the wheel speed sensor to the oscilloscope
02:23 Using the PicoScope 4425A to get the wheel speed sensor waveform
03:33 Adjusting the AC coupling oscilloscope settings to read the wheel speed sensor
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Great video, really appreciate that when you first show the oscilloscope waveform and it doesn’t look right that you show how to adjust the setting to fix it and explain it instead of just editing out that part of the video and showing a perfect waveform immediately.
Glad you appreciate the video Michael! I think it’s really important, these wheel speed sensors can be quite hard to get a signal sometimes. Thanks!
Excellent video, keep plenty of them coming. I bought a 2005 K74 L200 Mitsubishi Animal but when I plugged in a Launch 129E scan tool it came up with some fault codes for the front ABS wheel speed sensors. The reason the ABS warning light did not come on was because somebody had been inside the instrument cluster and removed the ABS light. The golden rule is always make sure all the warning lights come on momentarily when starting the ignition and check for fault codes before purchasing a vehicle. These magnetic ABS wheel sensors on this K74 pick up are so powerful they can even pick up a pair of vice grips so have no trouble attracting flakes of rust. I tried to remove a sensor but the flimsy plastic end on the sensor snapped off and I ended up having to remove the front wheel bearing housing to punch out the sensor, which had an extremely difficult to remove stainless steel sleeve. These Mitsubishi K74 pick ups have several versions of wheel sensor and giving all the vehicle information is no guarantee the correct sensor will be supplied. Even some of these DIY scan tools appear to be able to show accurate graphs and speed rates and just turning the front wheel by hand is enough to generated a signal on the graph. I cleaned the sensor on the other side with a long plastic cable tie to save having to remove it. Manufacturers design vehicles in the virtual world but would appear not to adequately test their designs on actual roads in the real world.
As far sensor that detect spinning objects:
Inductive sensors. Use an inductor in addition with a permanent magnet. Two wires sensor. Sensitive to ferromagnetic materials. Easy to test (even in the bench unconnected), it can detect really fast moving objects. Produces a sinusoidal signal. Really good as a CKP. Can;t detect slow moving or standing objects.
Hall effect sensors. Use a hall effect element in addition with a permanent magnet. Three wires sensor. Sensitive to ferromagnetic materials. It can detect even standing objects. Really good as a CMP. Produces a digital (square wave signal). Usually with an open collector output. Can;t detect (in a cheap form) really fast moving objects. Must be under power supply (usually +5 volts) in order to test it.
Magnetic resistance sensors. Use a variable resistance sensitive to magnetic fields. Two wires sensor. Doesn't need a permanent magnet. The spinning object must be an array of magnets. Really good at detecting position with great accuracy. Even really slow movements. Usually used as an ABS wheel sensor. Produces a digital (square wave signal with a DC offset). Must be under power supply (usually +12 volts) in order to test it.
This is superb bite-sized training. A lot of information on a wide variety of topics, but easy to understand, building from foundations upwards. This is engaging training that is perfect for beginners, but equally good for those who want to improve their diagnostic ability using an Oscilloscope. Great fun, clear, and relevant. Love the style, the clarity, and the pace. Having sat through the Free classes, it is clearly worth subscribing to more.
Great explanation as always Darren, thanks for showing this.
Very informative and clearly presented.
nice one Darren.....Darren 's online course is awesome, you wont regret it, money well spent, knowledge is key ... thanks Darren keep up the good work
Glad you’re enjoying the course Rob, looking forward to meeting you soon! 👍 Cheers!
Thank you for video
Darren, you are a wizard. Top work.
Hope you enjoyed the Pico course Matt! Got some more scope lessons coming soon 👍
Thanks for sharing Darren. I hope all is well. Will look into getting those adapters. I guess I could do the same test with the 2204 as were only using two channels. 👍
Yeah, it will still work in 2204a Artie 👍
Good job sharing
Glad you enjoyed the video. Thanks!
Hi Darren, great video by the way . . I had to replace these ABS pickup rings a few years ago on an E90 318i. BMW don't sell them separately but they will sell you two complete driveshafts at a total cost of over £1000 so i found replacement rings online and fitted them/changed the worn sensors. None of the local indys could figure out the intermittent ABS fault on the car so i got the job of figuring out what the problem was. I have just started using PicoScope myself and have found it an essential tool for modern vehicle diagnosis, many thanks for the known good waveforms, sometimes its hard to know if the signal you are getting is exactly as it should be!
Tried to sell you full driveshafts 😆. Yeah the ABS pick up rings are a good money saver! Glad you are enjoying the videos. PicoScope is a great tool!
Hey it was a good bit of fun getting it working , connecting it all up and seeing the that even though the sensor was catching it had no effect on the oscilloscope reading which you think it would have it was a really good day and I learnt a lot thanks Darren
I think I connected the leads up wrong the first time 😂
Glad you had a good day Jake, see you again soon! 👍
@@MechanicMindset ah that would explain the confusion at the start 😂 Atleast we got it done in the end and you got a decent video out of it see you at the next course
Nice one Darren
Thanks for sharing the post Stephen! Hope you’re good 👍
And the front ones are different. There are actually two types. One is active and one is like the rear one. Active sensor sends a heartbeat value every 150ms even when not installed on the car. Both types fit the same so it is easy to buy a wrong one. It is necessary to find out part number in realoem
On BMW i always check for rubbing on sensors on inspection/service and if customer complains about ABS/ESP kicking in at low speed or error codes
See it all the time here in Norway.
BMW only sell complete axels.
But you can buy the sensor ring for a VW Sharan and it is a perfect match 😁😂
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Just curious, in watching ATS videos with Bernie Thompson, he always states that you connect the negative lead to the battery ground as it is the lowest potential of the system. I noticed that you don't always do this (I know the E90 battery is buried in the boot). In practice, has not connecting to the battery ground has ever given you measurement issues? Great video as always, I didn't know that the pickups on E9X chassis do this, but from where I'm from we don't have a snow/ice, perhaps why I never noticed it.
For sure, battery negative terminal is always the best, but as long as you get a nice connection on chassis, it works just fine. Yes, I have had bad ground connections, you usually get a signal but it doesn’t look right; usually at the wrong voltage level and sometimes waving up and down (like it has coupled to mains 50hz EMF). If I get this I usually find a cleaner connection, or bolted ground connection.
I would say it is more important for battery negative connections when taking volt drop measurements 👍 (it’s ‘absolute zero’ Volts)
Awesome Darren,can you suggest a site that sells similar breakout leads, but for VW
Cheers Frederick. These are generic breakout leads. There are a variety of pin sizes. I use the same on my new Passat (which you haven’t seen yet!)
@@MechanicMindset eagerly waiting for it in the course... A real eye opener,keep it up
Thanks. Little fun, today at the gym, i listen to Sean Tippings pod about VR-sensors. He mentioned the problem with rust build up so the ring touch the sensor. But this is not a VR sensor or? I already bought your coures. Best regards from sweden.
No, this is hall type digital sensor. I think they used to use variable reluctance sensors on the same earlier vehicles. Hope you are enjoying the training! Thanks
@@MechanicMindset Thanks. I really enjoy. I am only a DIY mechanic, but i live on the countryside so i has the possibility of a large workshop. So its nice to nice to have the opportunity for professional education online, can not afford man to man courses when I do it as a hobby.
@@MechanicMindsethave you got the link for those jumper leads
Ac coupling can work on a good signal, better is to measure it against battery positive in normal dc mode( if signal is on the positive side). You will get a clean signal on a small scale. but most scopes don’t like that ( put a power on an scope ground). If you know how the sensors works and what can go wrong with the circuit this is the best way to measure it.
That will work nice, never thought to do it like that. To be honest, the zoom feature works really well on Pico, the AC couple is the safest way for all to use; like you say, putting positive on the ground can be dangerous for the scope and the car (if measuring more than 1 channel) 👍
I work with a 4 channel Tiepie differential automotive scope and this scope is ok with that, pico should also be ( if it’s differential) .
Another problem is when battery voltage will change, the voltage values on the sensor wil change as wel, not if you measure it against battery positive:)
Common as muck fault on several models. They even bring up a fault code for reluctor ring mechanical fault
I’ll be doing these soon 🙈
self adjusting airgap ;-P
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Great tutorial and Great Video thank you
Take care and have a Great Happy Easter 🐣 holidays and God bless you Mechanic Mindset
From Nick Ayivor from London England UK 🇬🇧
Cheers Nick, lovely weekend!
Great info mate. A lot of people get confused with the difference between active and passive wheel sensors.
Have you seen the latest sensors? True active sensors, directional and stationary signals…
@@MechanicMindset No I haven't, do you have any links for that info?
@@MiracleMAX Not off the top of my head. If I find anything I’ll send it over. You basically get a constant square signal that changes width with reverse direction
@@MechanicMindset Cool, thanks
Inductive abs sensors (the ones with the "crenellation" reluctor rings anyway) usually outputs a sine wave. Why the square wave in the video? Is it because of the different type of reluctor ring. I hope I make sense, english isn't my native language.
I understand. This type of sensor can work with a magnetic type ring, or a physical metal ring. Think like a camshaft sensor; square waveform, but the sensor picks up from the metal camshaft ‘ring’
@@MechanicMindset I've seen the same typ of rings (like the one in your video) on crankshafts too. So what you are saying is that with that type of ring (the one with holes instead of crenellations) you get a square wave similar to that of a hall-type sensor?
@@HerrDagerman If it’s being used with a hall type sensor, yes 👍
@@MechanicMindset Of course, by bad. Inductive sensors always shifts polarity (AC), so of course it's a sine wave :p
@@HerrDagerman Inductive sensors are usually a lot larger and heavier than the hall type 👍 easy way to tell
Hi Darren, is there any particular reason you didn't use the sensor ground and chose chassis instead?
The waveform would have looked a lot cleaner.
Interesting to see, just done one with a failed sensor and rustjacked reluctor ring, in my case the sensor had no signal output.
Changed the reluctor ring as it was in similar condition to the second one.
Interesting Simon, I was wondering the same thing.
Hi Simon, it’s the recommended way to connect. To be honest, it didn’t make much difference on this car 👍
I’ll be doing these ones soon! I think the main outcome is that the sensor head is eventually shaved off 😂
Why can't you back probe the sensor? Is it because of design of the connector or?
Yes, design of connector; it’s closed in this car to prevent ingress 👍
👍👏👏