I had an intermittant ABS light coming on in my 88 300E and it turned out to be a bad battery. When the voltage drops below a certain point (10 volts I think) the ABS system is disabled as it could become un-reliable. try checking your battery voltage and charging system. Mine was a shorted cell and replacing the battery fixed the problem.

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Dave
88 300E 250K Sold
2000 C230K Totaled @104K
2003 ML320 156K Sold
2009 E350 4Matic Sport 46K Sold
2011 ML350 60K Sold
2014 GLK350 46k Sold
2012 GL450 72K For Sale
2016 E550 Cabriolet 48K Sold
2015 GLK350 114K