The ABS light should go off when the fault which caused it's activation is fixed. If your light is still on it means you have a faulty wheel sensor or ABS unit.
The only other reason I know for ABS warning light activation is a faulty Overload Relay, first check the fuse on top of the relay to make sure it has not blown.
Overload relay is #92 in the first diagram ; http://www.detali.ru/cat/oem_mb2.asp?TP=1&F=129060&M=103%2E984&GA=722%2E363&GM=717%2E434&CT=F&cat=515&SID=54&SGR=080&SGN=04 .