All I have a 1996 300 tdi, and over the last few months the ABS light would go off as normal and come on again when it wanted to. If i restarted it reset it and was good for a day or 10 minutes. It was giving me the ****s. Anyway replaced the wheels 4 days ago and checked the sensors when the wheels were off. The right rear had play in it and when i pushed on the sensor it went in about 5 mm, not much but since i reseated it i have not had a problem, no light and great brakes again. Hope this simple check helps someone. Worth pulling the wheels of to check if you have this problem.