Hey guys just bought a new (to me) b5 A4. every other time i turn the car on my ABS lightcomes on and also it will happen while driving. The ABS system itself works fine with the light on and off. Any ideas as to what causes this and also how it can be fixed?
Thanks

 

There could be a number of causes. What seems most likely to me is that (due to being mounted on the underside of the car), you have one or more sensors that are either dirty or damaged as a result of road debris. However, it seems that people have also listed the ABS controller as having failed on them, and they're a fortune at the dealer. On eBay there are sellers that sell them remanufactured for a couple hundred dollars. Best bet is to find someone near you who has vagcom and can scan your fault codes to tell you what is wrong. Alternately, if you go to AutoZone or Advance Auto Parts, they'll scan them for you for free. Don't necessarily take their code definitions as gospel though - they'll pull the correct code but may not always be able to tell you correctly what it means (happened to me before). Get them to get you the codes, then you can use the Search feature here to find out what they mean, or type them into Google to find out.

Using Vag is more desirable - here's where to look to see if someone near you has it:

http://vag-tool.kicks-***.net/default.aspx

Find out what codes you have, and then we'll be able to help you more thoroughly with the diagnosis.