I have a permanent ABS warning on my dash. I have tried to use an OBDII scanner to diagnose it. However, the car does not support any error codes apart from engine management codes. Therefore I will have to use the old-fashioned way of using DMM and oscilloscope. After reading the following website: “https://premierautotrade.com.au/news/wheel-speed-sensors.php” I am under impression that the Honda Civic mk7 uses a passive wheel speed sensor considering a two-wire harness.
After viewing the following video: “https://www.youtube.com/watch?v=wnvrsY-UPf4” I would like to try to verify each sensor.
The frequency suggested in the video is 0.5Hz. At this frequency, the AC voltage should be around 250 mV. The AC setting of the DMM is optimised for 50-60Hz. Therefore, is the output of a WSS at a rate of 50Hz when the wheel is rotated at 0.5Hz? This would suggest 100 changes between N/S or teeth/gap. Is my assumption correct? Is the number of poles or teeth universal for all WSS? Lastly, what would be the easiest way to access the harness without fully lifting the car?
I have access to the ABS module in the engine bay. However, without a wiring diagram, I am not sure what to unplug and where to measure. Any hints are welcome. Thanks.
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You realize a typical OBDII code reader won't show you ABS codes? You have to have a reader which is designed to read ABS codes. These readers usually have SRS codes as well.– Pᴀᴜʟsᴛᴇʀ2 ♦Jan 4 at 14:58
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For two wire sensors, these are just Hall-Effect sensors, which all you're really looking for to see if they are working, put your DMM leads, one on each wire. Put your DMM to read voltage (lower range the better if available), then spin the wheel and look for the DMM to read anything. If the DMM shows some type of activity, the sensor is most likely working (very high probability).– Pᴀᴜʟsᴛᴇʀ2 ♦Jan 4 at 15:05
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I worked with Hall-Effect sensors passive and active in the past. This one being analogue output means that DMM would only verify basic operation. I would imagine that if the scope was connected (need to confirm the peak voltage of my scope) then I could see distortion in the sine wave generated when the sensor is detecting a broken tooth or clogged up tooth.– WintermuteJan 4 at 16:28
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I do realise that. I researched the OBDII in my car: mechanics.stackexchange.com/questions/89960/… I even considered sending HEX commands using the terminal facility in software I use for my OBDII scanner. I issue with that approach was that I could not find a reference to decode the errors.– WintermuteJan 4 at 16:33
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You don't need to see a waveform. You just need to verify it is giving output. You seem to be looking at it as an electronics engineer and not as a simple "does it work or not". Believe me, it just needs to give a signal. As far as OBDII, get a cheap scanner which will do ABS and you'll know what the codes are which is showing the ABS light on your dash. Again, you're taking the long way to get to where you need to be.– Pᴀᴜʟsᴛᴇʀ2 ♦Jan 4 at 22:18
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