I was checking a friends Skoda Superb from 2014, because he had some ABS issues. First of all the ABS indicator was turned on and second, some times when he breaks, the ABS system activates like when you break on a snowy and icy road, only it is summer.
I checked the car using live data on a scan tool, which showed the picture above. I thought that maybe it could be a half broken sensor. It was cheap and easy to change, so I thought that this would be a great way to eliminate that possibility. But nothing changed, so now I am considering a troublesome connection in the wires going to the sensor. But I do not have a wiring diagram, so before diving deep into a wiring system with blindfolds on, I thought that I would see if this could somehow be something else that I should rule out first?
Rust jacking of the sensor is another common cause. It takes very little rust formation to lift the sensor enough to cause signal dropout. Remove the sensor and make sure the seating surface is shiny metal, not rusty.
I had this problem on the driver’s side, front sensor.it turned out to be oxidized contacts inside the connector. I found out by accident when I unmated/mated the connector a few times and it worked again.
Thanks for all of the responses. The connector itself is not the issue. I already changed the sensor and had the connector off. It was seated properly and no oxidation on the contacts or surrounding the connector.
The wheel bearing is a good point, I would just have thought that any issues with a wheel bearing would produce dropouts with more consistent patterns. But I could try replacing it. Looking inside it is not an option. The wheel bearings on this car is sealed off and you have to replace the entire wheel hub.
I had the same issue with a Trailblazer. I used the divide and conquer approach. My scanner showed which sensor was dropping out at low speeds. So I disconnected that sensor and connected my DVM to it on AC volts. Then spin the wheel by hand and watch the output voltage. I could clearly see the sensor was not outputting the correct voltage and was dropping out. So I removed it and looked at the tone ring inside the hub as I rotated the wheel. There was some larger blobs of grease on sections of it I removed with a Qtip. But the real issue was rust had formed on the seating area for the sensor. A quick burnishing with a sanding disk on my drill and when put back together, all was well. Been working for a couple years since. Good luck.
I also wonder about the wheel bearing, but no need to replace it on a guess. Jack it up, spin the wheel and listen for roughness. Grab the tire and 3 & 6 and sharply rock it back and forth. There shouldn’t be any play.
I also wonder about the wiring. Spin the wheel with your scanner on it and jiggle, especially right at the connector. I had a go-round recently with an invisible problem right at a connector. This was a ground wire, and I had cleaned it all up and all appeared to be fine. But apparently right where the wire entered to connector there was some manner of fatigue/breakage going on that allowed it to randomly lose and regain continuity. But generally, eyeball the whole wiring harness.
It may be the toothed trigger wheel, but the wheel bearing itself it just fine. I already checked this, both by listening while driving and also by rocking the tire and listening to it using a stethoscope.
