OVER TCD and ERROR CM:MESSAGEs

Hi everyone there is A SHIMADZU GC 14 A WITH TCD Detector . when Turn it on appear The ERROR CM after that when press CE and working when we press TCD pushbutton in ON position the OVER TCD MESSAGE will appear... What is mean OVER TCD message when we Press ON pushbutton Over TCD controller ... And What is ERROR CM when Turning GC ON.. Is any body have Experience?? How can Fix IT?? Regards...