ok...here goes....2 weeks ago i decided to chabge my plugs....no big job....a day later the car ran like it had 2 cylinders down....come to find out about the wiring harness issues that mercs have and having disturbed the harness to the coils, the wires had given up......so rather than paying out for a new harness ... i made one....well worth a weekends work.......recconnected all to car and all was good...for a day....have now made a code reader for it(18 pin by the battery).....but cannot clear the codes that are in it...any ideas.....btw....the reader is suprisingly easy to make.......dave

 

ok disconnect the control unit that should clear the codes. no you have a d.m. n that car ok pull up the blink codes as each code comes up hold down the little button on the blink indicator for ten seconds then pull up the next code and hold down the switch for ten seconds repeat this process till all the codes are cleared if the codes come back on then you have a problem and need to fix the problem. also i dont know if your car is still running rough but in a few occurences that the shorted out harness kills your hfm control unit