ABS Wheel Speed Sensor Harness Repair Procedure - Questions and Answers

[uttevrec]

I started my 2013 S7 a couple of weeks ago and was greeted with a multitude of error messages: TPMS, ABS, Sport Differential, Parking Brake, Air Suspension, and Cruise Control. The code reader confirmed "ABS Wheel Speed sensor Open circuit/short circuit to ground" as the primary cause. Open/short-to-ground usually means a harness problem, but I decided to try a new sensor - even though the old sensor tested OK with my multi-meter (5.7 k-Ohms if I recall.). The new sensor had the same resistance...and didn't fix the problem. Not an easy fix. Must be the harness.

I next removed the right front wheel liner and started to trace the harness back. The ABS wheel speed sensor has unique plastic-coated wires with rubber grommets that fasten to the suspension at various points. That ABS Sensor harness merged with other harnesses, which merged with other harnesses. All of them are covered with fabric tape. I never found a connector to disconnect the ABS Wheel Speed Harness from the main harness. This is where I'm stuck. Here's a picture of where the ABS wheel speed harness joins with the other harnesses:

S7-ABS-sensor-harness.jpg

Does anyone know the official harness repair procedure? My guess is that I need to continue unwrapping the fabric tape until the ABS Sensor Wiring changes from plastic coated to standard wire. Then cut the 2-wires for the ABS wheel speed sensor there. Then splice in (solder / heat shrink) the new replacement harness. Then re-wrap the entire harness assembly with fabric tape. Does anyone know if this is the correct procedure? Am I missing something? Here's a picture of the replacement service harness from an eBay listing (I haven't ordered one yet):

S7-ABS-sensor-harness-new.jpg

[gk1]

Sorry, I don't know the procedure for that one.
I do see there are two part numbers for the harness (assume left and right). One appears to have a yellow, red, brown, and black loose wires, the other has just green and black like your pic.
4G0972251E
4G0972252C

From the wiring diagram green and black do appear to be the wires going to the right front wheel speed sensor whereas yellow and red go to the left front.
FWIW the one with yellow and red does appear to have termination pins on it like they connect into a larger harness somewhere. Not sure why the left front does not appear to be that way or maybe they want you to get your own pin termination kit. Rarely, if ever have I seen any Audi repairs recommend splicing or soldering. They almost always go to some termination point to replace. But that is just my 2 cents could be wrong. Plus if you splice and solder how do you know you have successfully fixed the faulty wiring or if it is further up from you splice. Just a thought anyway.

Assume front right


Assume front left


FWIW
Front Right should be pins T47/41 (black) T47/26 (green) on J104 ABS control module
&
Front Left should be pins T47/27 (red) T47/11 (yellow) on J104 ABS control module

Hope that helps a little.

[uttevrec]

Thanks for the pin and harness info. With that, I should be able to do a wire continuity test. (BTW, I think the front right harness is for both the wheel speed sensor and brake wear sensor, so 4 wires makes sense. There is no brake wear sensor on the left.)

I don't have the pin extractor or crimp/insertion tools anyway. i guess my best option is to order the replacement harness, unwrap the wiring bundle as high up as I can, and splice there. I can't figure out another option.

The harness failure most likely in the suspension area because that's where all the movement is. The wire break has to be internal; the harness looks fine on the outside.

[uttevrec]

Does anyone know where the ABS module is located?

[gk1]

Does anyone know where the ABS module is located?

I believe it is integrated with the ABS pump.

- - - Updated - - -

(BTW, I think the front right harness is for both the wheel speed sensor and brake wear sensor, so 4 wires makes sense. There is no brake wear sensor on the left.)

Good point. Makes sense.

[uttevrec]

I found it - you're right. It's in the engine compartment on the left side of the car by the ABS Module. That's a long cable run if there are no connectors in between.

abs-module.jpg

[uttevrec]

Upon further inspection, I found the failure point in the harness. It's at the lower-most rubber grommet that attaches to the suspension (on the side that leads back to the module, not the side that leads to sensor.) I'm guessing this is going to become a common failure as more cars approach 100k miles.

abs-wheel-speed-sensor-harness-failure.jpg

[Wiggs7]

How do you rectify the failure point? Entirely new cable, or just a section? I think I have the same problem 😅

[uttevrec]

You need to buy a new cable, which goes from the wheel speed sensor to the connector in the passenger foot well. You also need new terminal pins to connect the new cable into the footwell connector. (Remove the existing pins/wired from the connector and replace with the new harness wiring.)

[Ryan321]

Im going to bump this vs creating a new thread.

My car was hit and the sensor clip was totally smashed up (along with the knuckle). I have a new connector and sensor, however I do now know the pinouts for the connector. AKA There is pin 1 and 2. What pin goes with the green and black wires? I will post photos of the connector. Any help would be appreciated. (I figured this may help people with similar issues for this wheel speed sensor)

[IMG_0688.jpg

IMG_0689.jpg

IMG_0690.jpg

[Johnro79]

Hi there
I'm having the same problem and I need some help

Managed to unplug the abs module and look at my connector and pins
How do I know which is which? A6 c7 2913 2.0 tdi

[uttevrec]

It’s a 47 pin connector. Start counting pins from the corner going across, I believe from the upper left. But if the colors aren’t matching, start counting from a different corner of the connector. Also, there are usually tiny number molded into the connector for a few of the pins.

Front Right should be pins T47/41 (black) T47/26 (green) on J104 ABS control module
&
Front Left should be pins T47/27 (red) T47/11 (yellow) on J104 ABS control module

[Johnro79]

It’s a 47 pin connector. Start counting pins from the corner going across, I believe from the upper left. But if the colors aren’t matching, start counting from a different corner of the connector. Also, there are usually tiny number molded into the connector for a few of the pins.

Front Right should be pins T47/41 (black) T47/26 (green) on J104 ABS control module
&
Front Left should be pins T47/27 (red) T47/11 (yellow) on J104 ABS control module

holy crap
i was checking my abs module, not the J519. what a wally

i have pad sensors just on my left. does that mean that my module is on the left or same position , under the steering wheel?


EDIT: all sorted, was under the steering wheel. 20min job

[Daveywavey]

Does anyone have a photo of the footwell connector?

I have the same issue with intermittent fault on the right speed sensor. Changed the sensor but still happens, usually when turning steering wheel from lock to lock.

The wiring diagram just shows the direct connection from the sensor to the ABS control unit and not via J519 footwell connector.

[Johocke]

Upon further inspection, I found the failure point in the harness. It's at the lower-most rubber grommet that attaches to the suspension (on the side that leads back to the module, not the side that leads to sensor.) I'm guessing this is going to become a common failure as more cars approach 100k miles.

abs-wheel-speed-sensor-harness-failure.jpg

I had this exact same brake point. I measured from the J104 ABS controller and the connector at the ABS sensor and didn’t get a signal from the black wire. Upon further inspection the wire was lose inside the rubber mount as you pictured. Waiting right now for new cables that I can solder together inside the wheel well.