A4 B7 both rear ABS has faults. Help needed

[Andy. A]

My A4 has not been used for about 4 years and it's time for the Audi to get an MOT and become my daily drive. When I got the car it already had the two rear ABS fault codes.

Left rear ABS fault code 00290 status static and right rear ABS fault code 00287 status static.

Why does it say static, even when spinning each wheel fast by hand. Is this normal?

I also find it odd that both rear ABS sensors have a fault at the same time. Does this piont to another problem that can effect both sensors at the same time?

Has anyone else had this problem or can help me with this?

 

[Andy. A]

 

[Andy. A]

I took some pics and I might have found the problem. These 2 pics are from the rear left. I do not know if the right side looks the same yet.

Is the gap between the ABS sensor and ring too wide?

It looks like someone might have put a new sensor in on top of a lair of old rust without cleaning it off and the rust has expanded over time or it's just one of them things that can happen.

Might this be causing a wide enough gap to cause a sensor fault. What do you think?

The bolt to the sensor has rounded off inside, it is very seized and probably need drilling out and replaced with a new nut and bolt.

 

[Charlie Farley]

Both look like they have seen better days and no way they are coming out easily, most certainly a drill-out bolt and run a tap through the threads .

Do you have acess to vcds or similar diags to get a better over view on faults etc?
worth getting a decent scan done to see whats going on before attempting a fix even if they are both wll past it.

 

[Charlie Farley]

By the sounds of it , the problem is a bit of a long-standing issue if they were present when you bought the car.
Probably best to get a vcds scan and see whats going on under the skin for a better word.

 

[Andy. A]

I used the OBDeleven scan tool.

Came back with 2 ABS fault codes, left rear 00290 and right rear 00287.

Can you recommend a Tap set that will do the job?

 

[northpole]

well the faultcodes you got actually point to to much space between the sensor and the ABS wheel/ring but as said the state they are in means you won't be able to remove them without them breaking... luckily they aren't that expensive... just a royal PITA to get out.

 

[swisstony]

Cant advise on how to fix the problem but when you said the scan returned static , it has no bearing on the physical rotation. It is just the way OBD eleven returns its codes. Static usually means the code is present and cannot be cleared ( you tend to get an error when you do attempt to clear it ) as opposed to a fault code that OBD eleven can clear like an intermittent one.

 

[Charlie Farley]

In the final analysis and from a visual standpoint and the fact the car has historical issues with the rear ABS sensors, I would say you have just inherited the previous owners issues.
If you haven't used it for 4 years, that level of corrosion didn't just happen over night, one if not both were faulty and the previous owner was in the same situation you are now, he just delayed doing the repairs that you now have.

 

[Andy. A]

Found 2 new sensors on Ama*** at £13 each, a no name brand. Do you think these will be OK or can you suggest some that are cheap that has already been tried and tested to work alright?

Don't want to chuck good money away on a pita job like this. Rather do it once and forget.

Soon as I looked at the pics I thought it didn't look right and now the codes point to the gap too large. All makes sense now.

 

[northpole]

just get them and replace even if they last only a year that is a saving and a half... but look at GSF as they got their 65% discount going on at the moment... you might find a branded one that'll last longer for about the same price. i just checked GSF and the cheapest is from Hella at 23.16 each (that is with the discount)

 

[Andy. A]

I thought I would get the multi meter out and this it what I found.

I disconnected the ABS sensor plugs behind the rear seat left side and I got a 1700 M ohms reading. Is this the correct resistance?
I got no reading from the right side. Probably due to the wiring or a failed sensor.

I turned the ignition on with the engine off and with both rear sensors unglued from the harness I tested for voltage back to the ABS modul. It was 4.8V on the left and right, is this the correct voltage?

I have ordered 2 new sensors.

 

[Andy. A]

I have found the answers from a web site.
1700 ohms is good

This was posted by Voxmagna, Thank you to him. Hope he doesn't mind me pasting part of his thread here.

The ABS controller carries out two tests on the integrity of the wheel speed sensing system. At key on the controller looks for a 'normal' voltage on each sensor which should be 5V -- not 12V, zero or anything else. When the wheels are moving the sensor outputs are compared in real time. If a wheel pulse count is missing or one less than others, the ABS controller will fault. You can deduce that static tests at key on can be o.k but if the magnetic sensor ring or the tip of the sensor is damaged, a fault will be produced lighting up the ABS, traction control and tire pressure warnings.

Thought this might be good for anyone who is trying to find out the same answers as me.

 

[Andy. A]

I've fitted the 2 new Febi ABS sensors and the fault code has cleared.

I just need to drive the car to finish off the steering sensor calibration.

Thanks

 

[Charlie Farley]

Good news that's all sorted chap, just a shame the last owner left it for you to fix, but then thats just life with a pre owned car.

have a good one.

 

[Andy. A]

I now what you mean.

Hopefully it will pass its MOT OK. It's like going down a rabbits hole. I don't know what I will find next and there has been plenty. Still trying to sort some of it out.