Right I have found out how to do it, near the fuse box but just before it there is a black piece of plastic on its own that comes away to reveal a grey plug, its a 12-14 pin plug, there are two wires on there own, short them with the ignition set to acc for two seconds, then watch the display as the Engine Light/ECU light flashes the correct code.
Mine is coming up with 14 which is speed sensor, this happened after fitting a speed convertor which I have done many times with no problems, even taking the speed sensor off and reseting ECU has not cured my problem, any suggestions?