ABS Wheel Sensor Removal/ Replace

[Ryanic]

So I'm slowly fixing issues with my 1998.5 A4 2.8. Just got my cruise control finally working after 2 months of not having it working. It's now time to try and tackle my ABS light, Flashing Brake Light...Or as everyone knows. Non working ABS. I really want my ABS working before winter as I'll be living in Duluth MN...and if anyone knows that city, it's built on a massive hill....and it snows like crazy hah. 30% Declines are common. Anyways, looking to see if anyone could step me through step by step how to remove the front wheel sensors and rear on a 98 & 99 A4. I'm going to pull the wheel sensors from my parts 99 and just swap them out one by one and see if the problem is fixed. (When I bought the car from the previous owner he said a shop told him it was the drivers front wheel sensor or something and it'd cost about $100 to get it fixed by them. I'm hoping it's a wheel sensor but I know it might be my ABS module too since the previous owner wasn't too good with cars. So I'm going to swap my sensors first and cross my fingers it works.

I'm currently looking for threads online and what not on how to do it. But I'm confused on what part is ACTUALLY the part I need to replace... Guides with photos etc would be best.

I know the front there like a plug that you can just wiggle out/pull out, but that's about as far as I've come to looking into it. And I'm pretty sure that's not what needs to be replaced. I found this thread, but I have no idea what it is located on the front suspension. http://www.audiforums.com/forum/b5-m...or-out-152060/ I assume it's located under the plug on the fronts at least and in the rears I heard it's different.

All help is appreciated...Summer is coming to a end and I don't have much free time to finish up my to do list.

[Corrado_Guy]

The ABS sensors are easy to replace but if you live in the rust belt you will probably need to pry the thing out because they are a tight fit. Usually the flashing ABS/Brake light is the control unit and not the sensor but the first step is to check the codes and see what the ABS system thinks the problem is instead of just replacing things. For the record, ABS is not really all that great in the snow and it was designed to allow you to brake and turn at the same time. In snow it actually helps to lock the brakes a little to build snow dams in front of the wheels to help it stop a little better.

Take a look at your parts car and you will see an ABS sensor on each hub held in place by a single Allen bolt, remove the bolt and try to gently wiggle the ABS sensor out. It may help to paint it with WD-40 or something similar to help free it up but these can be a bitch to get out.

[ianwpb]

When my abs sensor went out the abs light and traction control light went on, not the flashing "brake" light. I would bet on it being the control module.

My 99.5 did not have an Allen bolt holding it in.. Not that it makes much of a difference.

[Ryanic]

Well I know the very first step is to get codes check, but I do not have a VAG-COM cable... :/ And if they're not to difficult to get to I don't mind just swapping parts at first.

I have no idea what I'm actually looking for... I always thought the part pictured below was the ABS Wheel Sensor but it's actually the Wheel Speed Sensor... So Yeah...


Also maybe I'll just try cleaning them all first before I swap them. I know people are using break cleaner for it but I don't have any at my house right now, any other fluid I could use? I have electrical cleaner Lol... else all I have really is water... with both are probably not a good idea?

[ianwpb]

That is the ABS sensor. It measures the wheel speed. Well, technically it measures the speed of the tone ring on the outer CV joint.

People refer to it by a few different names, ABS Sensor, wheel speed sensor, annoying sensor that gets chewed up occasionally, etc. Not to be confused with the Engine Speed Sensor or Vehicle Speed Sensor.

Again, I wouldn't go arbitrarily replacing ABS sensors. There's no indication that you have a problem with them. Not to mention, they aren't cheap. At least $35/each for the fronts on ECS.

[Ryanic]

I have a free all around pair from my parts car. Swapping them only costs me time. :P Then again I have no idea if the parts car ones even work.. But it's worth a shot. I don't mind tinkering with stuff and just swapping parts to test. If I had a VAG-COM I would just hook it up and have found out and the beginning of the summer lol.

But again anyone have any ideas on how to clean on my front sensors at least? I don't have any break fluid cleaner around.


Edit*
But now that I think about it... I need a VAG-COM to clear my dash lights correct in order to see if it even fixed it? Or if it's the ABS Wheel sensors will the lights just turn off and it'll work?

[ianwpb]

I have a free all around pair from my parts car. Swapping them only costs me time. :P Then again I have no idea if the parts car ones even work.. But it's worth a shot. I don't mind tinkering with stuff and just swapping parts to test. If I had a VAG-COM I would just hook it up and have found out and the beginning of the summer lol.

But again anyone have any ideas on how to clean on my front sensors at least? I don't have any break fluid cleaner around.


Edit*
But now that I think about it... I need a VAG-COM to clear my dash lights correct in order to see if it even fixed it? Or if it's the ABS Wheel sensors will the lights just turn off and it'll work?

The light will turn off by itself.

[Ryanic]

Success I found a photo of where the rears are located... Seems like a PITA to get to the rears though.

Does anyone know exactly how far the wires for the ABS Sensors go before they can be upclipped? I haven't look yet but I'm sure I can figure it out when I go to replace them. Just figured if someone knew off the top of their heads it'd be easier.

[ianwpb]

Success I found a photo of where the rears are located... Seems like a PITA to get to the rears though.

Does anyone know exactly how far the wires for the ABS Sensors go before they can be upclipped? I haven't look yet but I'm sure I can figure it out when I go to replace them. Just figured if someone knew off the top of their heads it'd be easier.

I'm not really sure what you're asking, but the front abs sensors plug in towards the top/rear of the wheel well. There's a grommet that you have to pull out and then you'll see a red and black connector (IIRC).

[DeltaAlpha9]

When I first got my A4 I had to do wheel bearings on the rear and absolutely destroyed the wheel speed sensors so you may be in for a fight. Then again I hate ABS at the best of times so the sensors are just zip tied to the lower control arm. The beeps/ flashing brake light tends to mean your controller is fubard.

[Ryanic]

I'm not really sure what you're asking, but the front abs sensors plug in towards the top/rear of the wheel well. There's a grommet that you have to pull out and then you'll see a red and black connector (IIRC).

Basically I was asking where exactly is the connection that I can unclip to remove the ABS wheel sensor completely from the car. And you answered correctly to the question I was asking. I'll look for the grommet that hides the wire connection point.

And I've always been under the impression the Solid ABS/Flashing Break is either or... Yes the module is like 80% times the actual fault but when I purchased the car the Previous owner said the shop told them it was one of the sensors or something in the front drivers side. So I'm going to go on that whim first before I dish out $100 for a new/used/rebuild of my ABS module. And again obviously I could always VAG-COM and find out in a second... But I don't have one..and I'd find a way to get my hands on one before I bought a new ABS/Rebuild to make sure it was my Module also.