Mondeo MA TDCi EML stays on

[madas]

Car has been running rough on and off lately and the EML has come on a stayed on. Cleaned out the spark plugs and now is running fine but the engine management light has stayed on.

Disconnected the battery for 20 minutes but is still on. Car has only 70,000 on it and starting to think that maybe the catalytic convertor is playing up as the rough running has been intermittent? not sure

Does anybody know how to reset the EML?