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Discussion Starter #1
I had an intermittent error on my rear left wheel speed sensor causing ABS/TC errors. Bought a $20 unbranded replacement and my scanner reports 0kph on that wheel at all speeds. Figured lesson learned don't buy cheap so bought a $40 AIP branded sensor. Still 0kph at all speeds. So I replace with the faulty original and I'm back to intermittent random wheel speeds and 'short to another valve' errors. Figure it might be the ground wiring or something so swap front and back sensors. Now the errors move to the front, so I'm now certain it's the sensor. So now I have a genuine ATE part on order. Weirdly the original and 2 replacements are physically identical and even have identical electrical resistance. Are these cheap sensors really this crappy or did I just get unlucky?
 

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I seem to be having the same issues that you are describing. I started getting a fault on the front left ABS wheel speed sensor (Implausible Signal - Intermittent) so ordered up a replacement from the local dealer. Swapped in the new sensor and am still getting the same error. Put on the scan tool again and saw the wheel speed sensor reading 0. Picked up a cheaper sensor from rock auto and then sawpped it in, same thing still, no luck.

I have checked the wiring, have 12V at the wheel speed sensor, have tried testing for a short by ohm'ing the harness out and wiggling it around at different spots and seems to test out good.

Were you able to fix your issue with the genuine ATE part? Has anyone else run into similar issues with the wheel speed sensors?

Thanks,

Chris
 

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Discussion Starter #3
Hi Chris, yes, 3rd sensor lucky! The ATE part from Pelican Parts ($52.75) fixed the issue immediately... Brand: Ate Part #: 7L0-927-807-B-M4

Easiest way to check it's the sensor and not a wiring issue is to swap front and back from the same sides... hopefully this will confirm its just the sensor

Cheers

Francis
 

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Thanks for the quick reply Francis, guess it's time to order a 3rd sensor!

I may attempt the swap the front and rear sensors, but the front was rusted in and ended up snapping in 2 pieces when trying to remove, so not sure if I'll have much luck...

Chris
 

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Following up on my last post and a bit more detail as I'm hoping someone can provide some additional info:

Wheel speed sensor fault on front left wheel. Scan tool shows 0 speed on the wheel, while others show speed normally.

Replaced with new OEM sensor from dealer. Same issue. No error codes at startup, start driving and ABS / stability control goes off randomly basically.

Bought cheaper aftermarket sensor from Rock Auto to try another. Error code thrown on startup, no brake issue aside from finding the front left wheel smoking after a short drive. Assuming brake may have been slightly applied or something. No ABS issue though.

Got dealer to warranty the first sensor, picked up and installed today, back to original symptoms with the first replacement sensor.

In addition to just swapping the sensors, after the first sensor appeared dead from the dealer I did the following:

1. Check resistance of sensor. Was in the .6-8Mohm range. Anybody know what it should be?
2. Check wiring harness. Have 12v at sensor. Putting the ohm meter on it and wiggling it all around look for shorts yielded nothing.
3. Hook up oscilloscope to look at the signal from the sensor and compared to front right sensor. The front right sensor put out clear pulses, while they seemed more random and less pronounced from the bad front left corner.

I have yet to try to swap around a wheel speed sensor as most likely it will not come out in 1 piece like the original sensor. The cars take a lot of abuse here with all the salt used on the winter roads and even though the sensor is plastic it sure got rusted in.

Anyone else have any thoughts? Is there any documentation on troubleshooting in the VW shop manual that anyone has seen / can share? Any way to test the sensor specifically?

Thanks.
 

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Following up on my last post and a bit more detail as I'm hoping someone can provide some additional info:

Wheel speed sensor fault on front left wheel. Scan tool shows 0 speed on the wheel, while others show speed normally.

Replaced with new OEM sensor from dealer. Same issue. No error codes at startup, start driving and ABS / stability control goes off randomly basically.

Bought cheaper aftermarket sensor from Rock Auto to try another. Error code thrown on startup, no brake issue aside from finding the front left wheel smoking after a short drive. Assuming brake may have been slightly applied or something. No ABS issue though.

Got dealer to warranty the first sensor, picked up and installed today, back to original symptoms with the first replacement sensor.

In addition to just swapping the sensors, after the first sensor appeared dead from the dealer I did the following:

1. Check resistance of sensor. Was in the .6-8Mohm range. Anybody know what it should be?
2. Check wiring harness. Have 12v at sensor. Putting the ohm meter on it and wiggling it all around look for shorts yielded nothing.
3. Hook up oscilloscope to look at the signal from the sensor and compared to front right sensor. The front right sensor put out clear pulses, while they seemed more random and less pronounced from the bad front left corner.

I have yet to try to swap around a wheel speed sensor as most likely it will not come out in 1 piece like the original sensor. The cars take a lot of abuse here with all the salt used on the winter roads and even though the sensor is plastic it sure got rusted in.

Anyone else have any thoughts? Is there any documentation on troubleshooting in the VW shop manual that anyone has seen / can share? Any way to test the sensor specifically?

Thanks.

What about the actual sensor pickup ring in the wheel bearing?
Don't know how it would become faulty but that is the other half of the ABS system ?

regards
Drag
 

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I'm still working on the above problem and am convinced the dealer has now sold me a second dead sensor. They are no longer willing to help me out unless I bring the vehicle in to them for servicing.

Stuff I have further tried:

Confirmed the pickup ring looked good and it does.

I am unable to remove the sensors in one piece as they are too rusted in, so removed connectors and temporarily extended wiring across sides of the vehicle. The error swaps sides along with the wiring. This would lead me to believe that the ABS module and all wiring is working 100%.

To further investigate the wiring, I removed the harness connector and test the wiring harness from it's connection at the ABS module right to the connector at the wheel. Inserting a 1k resistor at the wheel side read perfectly at the module side. Shaking, moving and playing with the harness and the reading was rock solid the whole time. Highly unlikely there are any issues in the harness.

Checked resistance values of all 4 wheel speed sensors. Original and still working sensors all read 380k, the new replacement read 6.5M, this is on par with the 1st one I got from the dealer as well. Something is funny here. I tried calling my local dealer again today to see if they would let me know the resistance range that this sensor should be, but they will not provide that information to me.

Does anyone know what the resistance range of a good sensor should be according to the shop manual?

Thanks.
 

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Just to follow up on this issue:

I was successfully able to get the rear sensor out of the left side and swapped the sensors front to back with no change in the error. This only left the pickup ring as the faulty part in the system. So went ahead and replaced the wheel bearing and now I am back to a functioning vehicle again.

Also to not, the old sensors with a 380kohm resistance reading and the new version with a 6.5Mohm reading both work with the system.
 

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What about the actual sensor pickup ring in the wheel bearing?
Don't know how it would become faulty but that is the other half of the ABS system ?

regards
Drag
Just to follow up on this issue:

I was successfully able to get the rear sensor out of the left side and swapped the sensors front to back with no change in the error. This only left the pickup ring as the faulty part in the system. So went ahead and replaced the wheel bearing and now I am back to a functioning vehicle again.

Also to not, the old sensors with a 380kohm resistance reading and the new version with a 6.5Mohm reading both work with the system.
An my question was valid :grin2:


regards
Drag
 

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Yeah, forgot to mention that Drag was right. I also agree with him on how does this part even fail...

After the bearing is installed how does it fail ??
But from personal experience I can tell you that the sensor ring can be made inoperable prior to install by contact with another magnet.

regards
Drag
 

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I know that this thread is a couple years old. I am just wondering how hard it is to change out the wheel bearing on the year. VCDS is showing that both rear abs sensors are not working. I swapped front to back and it says the same thing. This leads me to believe that the pickup ring is not working. I have googled how to do the hub but I am not finding anything.
 

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I have same issue in my 2004 2.5tdi touareg. Changed the bearing and at the same time broke the oem sensor. Now have tried two sensors and even put second new bearing in and no luck to get it working.

- wires are ok,

- 12V is coming to sensor


What could be broken or try just more sensors?
Short video how to change the bearing. Process it pretty easy, but you need the special tools to do it.

 
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