This is my experience with ABS system on my 93 SL2 a bracket on the front that suports abs wire to front wheel fell down and wraped around axel tore up the boot, had to replace boot , then noticed a bracket on back wheel was missing to,Guess what! They used what looks like aluminum rivets to hold these brackets on. well i tied the wire up on the back one and refastened all brackets with bolts, then the back wire that had hung down on back wheel went bad went to junk yard and found a new wire and a bracket and replaced that and lubricated all the plugin parts with a litle bit of silicon lube, what may help you would be to put small about of lube on these plugins near the wheels they may be dry or dirty and making a bad conection, Or you may have a bad wire on one of them, the wire they made these with is poor wire the one i had to replace i took the insulation off and the copper wire inside had turned to a black coroded powder. you may want to unplug and lube one at a time in case you have a bad wire it will probably make it worse and you would know which one it was that way.