Repeated intermittent ABS light issues

[Markiii]

Been getting repeated but intermittent ABS light issues, with accompanying ECP error over the last few weeks.

Pretty much in each case preceded by a bump in the road and a triggering of the ABS under braking.

Always self clears after teh ignition is cycled .

I'm guessing ABS sensor though who knows which one. Anything else likely to be the cause?

Pads and disks are pretty new and loads of wear left but generally I'm also notice a roughness under heavy braking if that possibly related??

[MikkiJayne]

Very likely a sensor if it clears itself. It could be failing or it could simply be dirty with rust particles stuck on the end so it is reducing the sensitivity. With these sort of faults you need to check the codes before cycling the ignition to catch whichever one it is, then you can dig deeper in to that sensor.

[Markiii]

thanks MJ are the 4 sensors all the same part number or are they different

[MikkiJayne]

Front (alloy upright) 4D0927803D
Front (steel upright) 4D0927803E
Rear 4D0927807B

[Ronin]

If its the fronts you can use this guide:

http://forum.a8parts.co.uk/showthread.php?t=16839

To save yourself ~£350

[Markiii]

thanks for that hadn't realised they were quite so expensive

[Markiii]

Originally Posted by MikkiJayne

Front (alloy upright) 4D0927803D
Front (steel upright) 4D0927803E
Rear 4D0927807B

thanks Mikki

would you know what the difference is between those for the steel and ali uprights other than part number?

[Markiii]

having had a look yesterday with the intention of giving them, a clean in the first instance.

it seems they likely have never been removed in 20 years and whilst I could get teh retaining bolt out the sensor remains steadfastly stuck in place.

Any tips for removal without destruction short of dropping the drive shaft and pushing from inside the hub?