Wheel speed sensor fault.

[Rfmotors1]

Hello,

I would like to share one older case where the vehicle returned few times with the ABS warning light ON.
By following the standard process, the technicians replaced, swapped, cleaned, checked and exhausted all the guided tests before the scope got it's turn.
We have lifted the vehicle, backpined the two rear wheel speed sensors and rotated the wheels. That was all we needed to do and we have found the problem. It was the wheel bearing with magnetic ring which had to be replaced.
Interesting is when we have removed the old wheel bearing and examine it, there was nothing visible, we have even removed the magnetic ring from the bearing to see it inside but it was visually perfect, clean, not any metal chips or uneven distribution of the small magnets.
I am thinking how much time and money could be saved by carry out this easy and simple test in the first place.
PSDATA file to open with Pico 7:

Wheel Speed Sensor.psdata

(2.75 MiB) Downloaded 27 times

Picture with notes:

[Bajzel]

Hello, some time ago I had an identical case in Astra J. I left this magnetic ring as a souvenir. The oscilloscope turned out to be worth every penny. Someone might be interested in the photos.

[Dan67]

nice use of the math channel I never thought to use it in that way to make a better visual que.

[Rfmotors1]

Hi Bajzel,
Thank you for posting the pictures, this magnetic flux visual foil is fantastic tool, I don't have it but used it few times at training.
It's fantastic tool to prove faulty part to customer, warranty etc. Much more direct as the waveform which not many customers can understand.

Hi Dan67,
I agree, the way to use math channel to find irregularity of signal is not common. I have used it on wheel speed sensors and crank sensors as well. Sometimes this is the easiest way to see the problem.
Simply zooming in may not be visually recognised as fault. The math channel reveals the repetitive pattern so one knows where to look.