G46 Rear left wheel speed sensor problem

[Jay-Jay]

Hi everybody,

I'm experiencing a very strange problem.
While driving, randomly the ABS-ESP-TPMS lights come up on the instrument cluster, anticipated by a little alert sound.

VCDS says there is an "Electrical fault in circuit" related to the rear left wheel speed sensor (G46).
So, I did these things:
- I checked the condition of speed sensor and hub (everything was apparently ok);
- I replaced the speed sensor and the hub (it did not fixed the problem);
- I checked the speed sensor's wire (it doesn't look damaged).

There is not a particular way to replicate the problem to make the error comes up when I want.
It's completely casual, no matter if I drive slowly on a perfectly flat street or on a street full of little potholes or if I drive at higher speeds.
Sometimes it appears after only few mt since I started the engine; sometimes it appears only after many km (10-20km).
I recorded a log with VCDS, while monitoring in real time all 4 wheel speed sensors: when the error comes up, the ABS Unit suddenly stops to communicate with the rear left speed sensor.

Any suggestion on what else to check is really appreciated.
This problem is really making me crazy...

[iichel]

Verify the wire end to end, so from the ABS unit to the speed sensor with a multimeter. Do this in normal condition and also wiggle it around a bit. Check connectors for corrosion.

A second option would be to temporarily install a second wire from abs to G46.
If the problem persists, the ABS unit might be broken.

[Jay-Jay]

Thank you for your suggestions!
I'll keep this thread updated.

Inviato dal mio MHA-L09

[Jay-Jay]

Problem fixed!
I've found a crack on the sensor's wire immediately under the rear left seat, right before the wire enters into the car.
After repairing it, the problem seems to be fixed.
Now the ABS Unit communicates with all 4 sensors and can read the speed of each wheel with no interruption.

Hope this thread will help someone else with the same problem.

Inviato dal mio MHA-L09

[RUM4MO]

That must have been a bit annoying and cost a bit of time and money! Can you think of a good reason why that section of wire got damaged, is the cable too short at that point, or do you think that you have damaged it by driving over something on the road and it was thrown up against that section of cable?

I think that I've noticed in pictures on one of these forums that the ABS wiring cable did look like it was not very well protected against any objects that might get thrown up from the road. I'll need to look at how these cables are routed on my wife's August 2015 Polo SEL while I am cleaning out/servicing its brakes before it gets its second service next month.

[Jay-Jay]

The damaged section of the cable was very short (about 3-4mm).
Since that section is located very close to the exhaust (which becomes pretty hot) and considering that I have lowered the car (B12, -3cm), I guess the cable started to be in a different position respect to what VW has designed. But I lowered my car 3 years ago: it's strange the problem has appeared only now.
Another hypothesis is that a cat could have played with the cable (recently I've seen a cat sleeping under my car).

Luckily, fixing this problem didn't cost me anything, because I already had all the necessary material.

Inviato dal mio MHA-L09

[iichel]

Thanks for the feedback!