my engine managment light was on origionaly when i bought my focus rs because of the decat system, i plugged a mil eliminator which i bought from ggr in line with the lambner sensor to stop the engin man light coming on. i disconnected the battery, left for half an hour plugged in the mil eliminator reconnected and the light ment out. great! but after halfhour driving it came back on??

do i need do have a diagnostic or will it go on its own??/


help please

cheers guys