UK-POLOS.NET - THE VW Polo Forum

Hey guys,
The mrs car had rear driver side ABS sensor that was giving a faulty reading which led to the inevitable TPMS/Traction Control/ABS lights on the dash.
I replaced the sensor, cleared the DTC's and the warning lights all went away.
We put it through MOT which it passed.
She drove it home from MOT and the lights came back on.
I plugged in my OBD which cleared the codes, randomly it cut the engine out and all lights gone from dash again.
Next day the lights are back on.
I took the sensor out, cleaned it and the area it fits into and all was well again for a couple of days until it came back on again.
The rear driver side is a hub without brake discs.
Now it does sit for weeks at a time and occasionally I do have to shunt it into reverse to free up the sticky rear callipers.
What I am getting at here is; do rear hubs without brake discs have ABS reluctor rings which I could change as an option or could this be down to the sticky callipers?
Thanks in advance

given that it's a drum brake, I'd rule out sticky calipers.
the abs magnetic ring is part of the wheel bearing, which can be swapped relatively easy. if you're positive the new sensor is OK and no damaged wiring, it might be worthwhile to check the magnetic ring.

but removing the outer drum a bit more complicated than taking of a brake caliper, there are tons of YT videos on how to do so.
perhaps your friction material simply needs some aligning:

https://www.youtube.com/watch?v=1cVZWH6AAvc

Have you made sure that that rear hub bearing is not worn, ie worn enough to allow the distance of the magnetic ring to move too far away from the sensor.

I reckon there is less chance of a rear bearing being worn than a front one, but VW Group seems to like using suspect wheel bearings in my (small) experience.

By the way, which brand of ABS sensor did you fit - just really out of interest and to add more detail to this issue?

Thanks for your help and advice guys.
I fitted a sensor from Europarts rather than an OEM in a mad rush to get it through MOT before expiry.
- The rear wheel bearing sounds fine however I will inspect for sure.
- Will re-check the sensors wiring to be sure its fine and run diags to see that its giving a good reading.
- if I am then positive the new sensor is OK and no damaged wiring I will check the magnetic ring.
- As you say removing the outer drum is a bit more complicated than taking off a brake caliper, so will follow Youtube video to do this.
- I will also check the suggestion that perhaps there is friction material that simply needs some aligning.

Thanks guys and will report back soon!!! Legends.

I thought that I was doing the right thing when I ended up with breaking a front ABS sensor when changing the front hub bearing assemblies, and headed to ECP and bought a Bosch branded ABS sensor based on Bosch being the manufacturer of the ABS controller, when I removed the broken/damaged ABS sensor I discovered that it was branded TRW who will be the company that supplies the pre-assembled brake/hub units to the factory assembly lines, these did not seem to be rebranded Bosch items as the bush/ferrule that the securing bolt passes through were aluminium alloy on the factory fitted TRW version whereas the spare or aftermarket Bosch version had a brass bush/ferrule that the securing bolt passes through.

Unrelated maybe story time:- Years ago, when Vauxhall (GM branded cars in UK Opel elsewhere) just made a mess of fault finding my car that was under warranty, to ended up taking an oscilloscope home and probed the individual ABS sensor outputs, in my case, at the ABS controller connector, and then rotated each wheel and found that all the sensor had roughly the same output amplitude and waveform, in that case it was the ABS controller that was faulty, but this was before Bosch had built in the ability to test these controllers on the car and in a workshop, my dealer just dismissed what I had found and continued to replace ABS sensors in this order, front rhs, front lhs, rear lhs, rear lhs, both front sensors - then admitted defeat and replaced the controller, that p--sed me off as it meant 6 or 7 visits each time driving away and the system self testing and failing, and me phoning the garage after getting home from being at work - idiots! Plus each of the original ABS sensors which had alloy cans like capacitors, were fitted with a plastic or ptfe sheath to protect them from corrosion as they were pressed into cast iron assemblies - so that car ended up with 4 small time bombs just waiting to fail because the workshop was stupid, only one failed later in my ownership, but the other 3 failed while the next owner had that car.

Wow man, top advice and thanks so much for the input from you all.

I will take some time toward the weekend to get to the bottom of this and will report back.

I cant thank you all enough for your inputs

What I forgot to say was, as the ABS controller with located in a very convenient point in that Vauxhall car - it was in box under a cover on the front passenger side sill area, I unplugged its connector, and using the wiring schedule from my Haynes repair manual, I identified each of the 4 wheel sensors wiring, so checking the individual wheel sensor outputs was very easy, after doing that I used a high impedance multi meter and checked each of the 4 pairs of signal contacts "looking back into" the controller - ie each of the channels, one of them had exceedingly high input impedance, the other 3 had roughly similar much lower input impedance - but my master tech at that Vauxhall workshop could not make use of that information - so wasted lots of warranty time - and my time!

After I made a fuss after it was handed back to me still faulty, the workshop manager "test drove" that car after each of the following attempts to repair it, and passed it as being fixed! Each time it then failed again, I just continued driving home as I don't think that that garage would have given me a loan car, and I wasn't planning on spending over an hour on a bus each time they failed to fix it. Of course to make things even worse, this ABS failure happened during winter weather so ice on the roads, just the time you do need ABS!
These systems need a minimum length of distance travelled before the system perform a self test, back then it might have been 400 meters or so, nowadays the ABS system performs a self test within maybe 20 meters.

'Recently' a forum user bought this SET on Ali at a fairly affordable price and it did quite well, solved his problem.
viewtopic.php?p=598211#p598211

Blessed experiences:
@RUM4MO ...❄🌨... I don't even remember how many of these experiences I had to go through. Thanks for sharing.
(the mysteries of life...)