1997 Pontiac Sunfire ETS light on

Hi, im a A.S.E certified tech and work at a repair shop.we've had 3 cars in the last 4 months,97 pontiac sunfire,99 sunfire,2000 cavalier,all with identical problems.The ets light stays on and won't shut off with the button,the check engine lites on all 3 cars,and with my limited diagnostic eqipment the ecm,s don't want to communicate with either one of our scanners(matco code reader and OTC code reader with some live data.HELP PEASE! Thank's, Steve (C.E.O/lead tech).