Audi S2 Coupe 3b 1991 Abs Problem!!

[audimaniac]

Hi Forum members, after trawling through many posts regarding ABS problems, i could Not find my exact answer, so here goes, hopefully, someone can pin point my cars problem??
A couple of days ago after no problems what so ever in 9 years of ownership, i came off the motorway and **** myself!!! as i had a solid brake pedal and the brakes would Not stop the car!! There was lots of pedal feedback and noises from the ABS!!
What is strange to me now, is that, when i press the ABS Switch on the dash, the ABS light on the clocks illuminates and the brakes are spot on again?? Distinguish the ABS switch on the dash and all goes to **** again???
Can anyone suggest what the problem could be??
Any help would be appreciated.
Regards Audimaniac.

[UrS4boy]

Because pressing the ABS switch disables the ABS computer and everything "works" again (well except ABS), it would appear that your brake system is probably fine. Following from that I would have to guess that either the ABS computer is fooked, the connectors to the ABS computer are fooked *OR* one of the ABS wheel sensors is totally fooked.

PN is 857907379D Item 1 below Lots show up on a google search and then "images". Should be under the back seat bottom.

[domas]

Based on the symptoms, one of your sensors is seeing a very different speed.
For easy diagnosis you need an oscilloscope or a KDAS0003

[taren86]

I think one of your sensors ore ring have a big gap between sensor and abs trigger. Tried just knock the sensor slightly. Me by is just cam off.

[GazzaG60]

not too much or the abs teeth ul chew the sensor up

[audimaniac]

Audi S2 ABS Woe's keep going on an on!!!

After previous attempts sorting my ABS problems, i still have woe's going on!! I don't get much spare time these days!! Taken another look at my S2 this week, i canno't seem to fathom out it's problems!! Start up the S2 and no lights appear, press the footbrake whilst starting and my foot sinks down as if the Accumulator/Bomb is working fine?? Set off moving and i get a solid pedal and rubbish brakes!! Then the pedal sinks a bit and Brakes are restored fine but ABS Light is on again?? Done the Bomb test and soon as my engine go's off, i tried the test and i have a solid pedal?? All sensors seem ok?? Any ideas guys?? Thanks in advance.