I have had a few issues with the dash warning lights coming on with warnings for Power Steering, TCS, ESC, ABS, Bulb failure and Tyre Pressure all at the same time. Plugging in my OBDII device it checks for error codes and one code that is not an actual number is for the left-hand rear wheel sensor which is the ABS sensor. I switched over onto live data setting on the OBDII  and selected ABS sensors mode and drove for a short while and observed the readings, all 4 wheels were turning at the same speed?

 

So I cleared out the codes and all seemed OK for a few weeks and then the same thing again happened, cleared the codes, all OK

 

Next I searched the web looking for clues and I came across this video of a person having similar problems with his Octavia so I pulled my N/S rear sensor and checked its resistance value and it 7.5Mohms and in the video he says the resistance of his faulty one was 10Mohms and his new replacement was 50Kohms. So based on that I went and brought a new sensor made by Hella, not a China knock off, and before fitting I measured the resistance, and it reads 3.5Mohms.

 

So I have not yet fitted it as I don't want to fit it in case it is faulty, so does anyone actually know what the correct value should be?  I have been through the downloadable purchased workshop manual, and it does not give that information.

 

 

All I can say is mine turned out to be the hub ring starting to break up

Thanks for the reply, how many miles had yours done at that point and was there much rust around the wheel area? Mine has zero visible rust anywhere that I can detect so far, and all the hub ring videos I have seen appear to be very badly rusted.

Hi 

I broke the sensor trying to get it out so had to take the disc off.

Thats when I thought ****e it’s the hub, sections missing etc due to rust and breaking up 

maybe around 70k ( can’t really remember) 

wasn’t much visible rust to be seen, just the thin metal of the abs ring 

Edited 16 April, 20224 yr by Snapper1725

Mine was the rear hubs breaking up too, 160k miles on the clock. First one side followed shortly after by the other side.

 

Can't help with the readings on the sensor though

Well, after reading these reports, I decided before going ahead and fitting the new sensor I purchased that I'd do some live data testing with my OBDII device plugged in. Drove it around the town a couple of times and the data never missed a beat, all 4 wheel sensors gave perfect results, so that to my mind should really confirm that both the sensor and the hub ring must be OK and the message I'm getting from the device is a generic one. I have saved screen prints of the fault codes which I have the following:

 

18255 Please check DTC memory of brake system ECU

0047 TV-Tuner (R78)

13637396 Manufacturer-specific code (tap to search)

13705985 Databus - Received error message

01316 ABS Control Module

02214 Tyre pressure warning

00290 Left Rear Wheel speed sensor (G46)

 

So armed with this data, is it best to book it in and let the garage run through and cure the problem?

If you haven't already, I'd delete all the fault codes and then use it for a day or two and then re-scan and see if any of the codes return 

As above 
But since you have said you have already cleared codes
I would stick a sensor in 
There not hard to do

00290 code

The fault in 00136 abs control module is because there is a code needing cleared

The Tv always comes up🤪

Edited 19 April, 20224 yr by DEL80Y

I’d say left rear 290 

Thanks for the feedback on this issue, here is the current status of the problem. I have cleared the error codes 3 or 4 times now and the problem goes away. It can be clear of errors for weeks at a time and then suddenly it will strike again. Clear the errors, and it can then either come right back on again, or it might be clear for a few miles / days before coming back again.

 

It is always the same codes each time, and it always mentions the rear N/S wheel sensor and each time I have switched over to live data and driven for while observing the live feedback from all 4 wheel sensors, which always comes back with all 4 sensors reading the same values.

 

I Googled the results about the N/S rear wheel sensor, and it came with many YT videos on the problem, suggesting that I should use a multimeter to check the resistance of the sensor and the general view was that a value of several Meg ohms was not acceptable. One video suggested it should be around 50K ohms, and a manufacturer of ABS systems, own channel, said that the average reading should be around the 1K ohm, I was reading 7.5M ohms on the one fitted.

 

I went and purchased from GSF motor spares, one of their Premium range sensors at a cost of £39.90 after their Easter discount and before I set about replacing it, I measured its resistance, and it came in at 3.5M ohms, and I thought WTF, this looks faulty going by the YT videos were suggesting.

 

After looking into it in a bit more depth and asking on an electronics forum, it seemed that the sensors are Hall Effect sensors and that these could have various resistance values as they contain microchips inside the sensor body itself and that these chips, given the current global shortage of microchips, might have slightly different chips fitted and hence the different resistances, but still function OK.

 

The car has been bottomed on a couple of occasions while been driven slowly over rough ground, so it may have damaged the cabling under the body, the cabling in the wheel arch is fine. Couple this with the fact the live sensor readings has made me come to the decision that the problem might well be under the car and that I cannot access it any more because of my age, without a pit or a lift, so I have booked the car for a full diagnostics check with VW group specialists using the same software as the factory, to investigate and cure the problem.

 

I have reservations about it being on the wheel at all, be it the sensor or the reluctance ring on the hub, for the reason that if the ring had damage then it would be showing up when doing live data readings, and with the vast amount of potholes on our roads, especially in Essex, constantly jolting the car, some which really make the car shudder with the impact, could be making any damaged cabling make intermittent connection problems and setting alarms off again.

 

So I have returned the purchased sensor for a refund, as I might have ended up fitting it, and still having the problem, then replacing the reluctance ring and still having the same issues, all the time building up the cost, and still having to resort to the garage who has the equipment to resolve it for me at extra cost. Had the live data tests shown up an issue coming from the N/S rear wheel, then I would have replaced the sensor with the new one. But without being to pinpoint that the issues was indeed at the wheel, I might just have been building up the costs unnecessarily, which is something I need to avoid being a pensioner.

 

I think you all for your inputs, when the garage has concluded, I'll let you all know the outcome, but won't be until next month now when they get around to looking at it for me.

The last ABS sensor I dismantled had zero electronics in it just a coil wound around a metalic core, the system looks for a change in the magnetic flux as the sender wheel passes the sensor so inducing a voltage pulse 

Would need 3 connections for an active sensor of any type, I think?

26 minutes ago, nige8021 said:

The last ABS sensor I dismantled had zero electronics in it just a coil wound around a metalic core, the system looks for a change in the magnetic flux as the sender wheel passes the sensor so inducing a voltage pulse 

That is precisely what I thought the sensor consisted of, but no, there is electronics inside them for sure, they are 100% polarised and the positive and negative of the supply must go to their dedicated pins on the actual sensor. I tested the sensor using my Fluke 85 DMM and the resistance specification of that meter is upto 40Mohm and the sensor when connected one way round (and they are only 2 pin sensors) gives a reading of O/L (in excess of 40Mohm) and when the connections are reversed, reads 7.5Mohm. A straight forward coil is not polarity minded.

32 minutes ago, Pete_Ex-Wino said:

Would need 3 connections for an active sensor of any type, I think?

That is exactly what I thought and all the examples I could find on YouTube also stated that, but there are indeed some new sensors on the market that are 2 cores only, and so they must rely on the ABS control unit to act as their load.

Hmm, I'm unconvinced.

What could possibly be responsible for high-resistance readings - no offence intended - is difficulty in getting meter probes reliably onto sensor pins which might be deeply recessed in housings?

 

Not when you have small croc clips that are directly onto the 2 flat pins which protrude from the sensor and then to prevent accidentally disconnecting a connection in the small sensor housing, you unplug the banana plugs from the meter and reverse them.

 

The lead which plugs into the sensor has 2 recessed sockets that the 2 flat pins enter to make contact. Using the meter probe leads instead of the croc clips, reveals that there is no power to the sensor until the engine is actually running.

Edited 19 April, 20224 yr by Graham Butcher

Fair enough. 🙂

Yeah, I don't know if the first Superb is the same or not or indeed what other cars run with. This is the first time I have had to physically interact with a car for over 40 years as I have always had company cars  in the past. Infact my current car was my company car which I purchased when I retired 6 years ago. So this is a steep learning curve for me.

Edited 19 April, 20224 yr by Graham Butcher

Wiring diagram does show a + and - next to the sensor connections too, now that I look carefully.

You're winning me over. Perhaps there's a diode in there, although it's just shown as a blacked out resistor shape in each.

Like this one:

Active devices usually show a transistor symbol to indicate such?? 

Please do a post mortem dissection on one if you do end up replacing one. 

Edited 19 April, 20224 yr by Pete_Ex-Wino

Yeah I thought there might be a diode, but what would be the purpose of that if there is just a coil and magnetic core within it. I'm not going to be replacing it, if it does get replaced, it will be the garage doing it, so I'll try to remember to ask them for the old sensor back in order to try and dissect it, if they do replace it. I'm intrigued to learn its secrets as well.

 

Where are you reading the circuit diagram from? I have downloaded one, but I don't recall seeing the ABS system in it.

Edited 19 April, 20224 yr by Graham Butcher

1 minute ago, Graham Butcher said:

but what would be the purpose of that if there is just a coil and magnetic core within it

No idea! Diagram added to previous post by edit btw.

See what readings you get on a 'diode' range of the DMM?

 

Thanks for the info, where did you get the wiring diagram from?

The one I read pertaining to your car (well Superbs of that age in general) was bought from erWin a while back, the one that above screenshot is from was wild on the net somewhere as far as I recall.

1 minute ago, Pete_Ex-Wino said:

See what readings you get on a 'diode' range of the DMM?

 

I no longer have access to a sensor without ripping my wheel off again, and I'm not planning on that again anytime soon, I'm not as agile as I was once. Years ago popping wheels of a double-decker bus posed no problem for me, that was where I did my apprenticeship, with what was then the National Bus Company, as an Auto Electrical Engineer. Now 73 and way out of condition and to big for this game.