I clipped a kerb with a rear wheel a couple of months ago, a minute later the dashboard lit up like fault code city & then gradually all the lights (ABS, ESP, 4WD, TPMS, Steering assist etc) went out, this started happening more and more often.

 

The common fault in VCDS was always an intermittent signal from the left rear speed sensor, all the other lights & codes I believe were systems that needed the speed input to function.

 

Recently the dash would light up after driving 50 metres and now a TPMS light flashes as soon as the ignition comes on and when the fault code is erased it comes back immediately, I believe the sensor now is open circuit and the TPMS does a self check of all of them on start up before the vehicle even moves.

 

Enough background, I want to know if its the sensor or the reluctor ring in the bearing assembly that is the problem, I removed both rears with the intention of swapping them to see if the fault moved but they are handed.

 

I checked the output using measuring blocks on VCDS and there is nothing coming from the left rear wheel sensor.

 

So I checked the wiring to the connector and it was getting a solid 12.3v even when the cable was taut and flexed, I then measured the resistance across the 2 pins on the sensor and got a very high resistance, 0.3 on the 20 meg Ohm range.

 

I connected the sensor to the lead but removed from the wheel hub, with measuring blocks monitoring its output I waved a magnet to and fro beside it, no output, then I tried a piece of steel, same result.

 

So do you think it is the sensor or the reluctor ring or is there another way of testing to decide which?

 

If the bearings are not handed I dont mind buying one & keeping it as a spare but the sensors are handed and I dont want to waste money if it is not that.

 

Many thanks in advance.

Whilst they are handed it would appear that both front and rear sensors are the same so tomorrow I will try to coax the front one out of its rusted burrow to swap front to rear.

Easier said than done, I fear, and you've said it might be tricky.

What about trying the magnet waving on the rear sensor (extracted) that seems to be working, to test your test technique?

I thought of that but having already removed and refitted the good one after finding that they were handed I could not face removing the wheel again

 

But you make a good point, they were very difficult to remove last week and I put them back in with copaslip so better to try and learn with the rear one that I know slips out than risk breaking the front.

 

I'll give it a go, I'm curious to see if the test technique works and I reckon you are too!

 

The magnetic ring (now I know its name) might still be dodgy on the bad side so if the test shows the sensor is gone I will probably still swop the (good) front to the rear to ensure the magnetic ring is functioning.

 

I might even remove the hub to declag it.

 

If I were still in the UK I would have bought 2 sensors and 2 rings before even touching it, not only do I have to add very expensive delivery from Ebay UK suppliers on each item (no grouping) but then I have to pay frais de Douane on top, pretty much doubles the price, even sensors from Germany want €25 delivery

If the code comes back immediately without movement I think it would most likely be the sensor, but then again a large shock is more likely to damage the bearing than the sensor .

 

I'm 50/50 at this point.

 

 

 

 

My thoughts exactly!

 

The problem is that the code which comes immediately without the wheel turning is one for the TPMS control module no comms I think.

 

For a start I dont think there is a seperate TPMS module as its not on my installation list and I cannot interrogate it, I think its within the ABS or body control module and the fault is that it does not see all 4 sensors during the pre start check.

 

Swopping the sensors around would still bring that fault but without knowing from which wheel.

The shock may have dislodged some rusty flakes which in turn stuck to the magnetic ring, or it may have cracked the ring or flaked some of it away if its rusty, by all accounts it can just be seen from behind the disc dustcover.

My money is on the sensor failing. Especially if you have warning lights on before you turn a wheel. ABS ring pretty low tech and nowhere much to go without being an obvious fail.

Learned a lot more today.

 

Pulling the plugs from each individual sensor gives a fault code of wiring circuit (or something like that) so both sensors are being seen by the controller with the wheels not moving.

 

No resistance was measured on the good RH sensor so that is a false piste.

 

The good sensor reacted to me waving a magnet at it 👍 so that is a good diagnostic tip.

 

Conclusion is bad sensor on LHS, magnetic ring is not visible on the 4x4 model so is probably better protected against foreign bodies and corrosion, new sensor ordered, cost €13.90 inc delivery, it will be a cheapo pattern part but we will see.

 

The fault code that comes up without turning a wheel is 01325, comms failure from TPMS module which is within the ABS module, I am hoping that it has simply stopped communicating as it no longer has any LHR wheel speed data, I am hoping with the new sensor it will relearn the wheel speeds and start communicating.

 

We will see, in any case the sensor replacement is the first priority, I will test it with the car in the air with VCDS initially.

I ordered the wrong sensor by mistake, got the correct one today and all warning lights now extinguished 👍

 

It's interesting with regards to the parts prices, I did not return the incorrect one even though it was allowed because the cost of me returning it and of them sending it out in the first place would have exceeded the value.

 

The new one was only €9.46 and the sender, a business sending out thousands of auto parts had paid €7.40 for postage as witnessed by the stamps used.

 

The part and jiffy bag weighed less than 20 grammes, no wonder my country is in such a state when they screw the citizens and businesses to that degree but allow special low postage rates for Chinese imports, I could have made 5 seperate purchases and recieved 5 deliveries to my door from China for the same price.

 

The seller will not have paid any more than 50cts - 99cts for the part, how much do Skoda shaft you for? Breezy Pete will know, the correct part number was WHT003857

I hope you have more luck with cheap sensors that I have, I would go OEM every time, it saves a lot of hassle 😉

We will see.

 

Once the original one was coaxed out and the hole honed out fitting a replacement is a 3 minute job with the car on its wheels so no hassle at all to me.

 

Now you have made me think of it I am going to order a couple of the real cheap Ali-Express ones to keep in stock.

Not a bad idea for the price of them, if you do though it is worth at least plugging them into the car because I have had them dead on arrival before.