Disco II abs & srs light

Been having the abs, tc, hdc and srs lights on the dash. So far have checked the wheel sensors with a dedicated tester, which cnofirmed all sensors ok, also checked them with an ociloscope. The lights all come on at the same time, which leads me to suspect that as the srs and abs ecu's are seperate, could a duff earth cause this sort of fault? The time period before the lights iluminate is after 1 to 5 miles and sometimes instantly once the vehicle moves. The abs still functions, and brake performance is not affected. Any help or advice greatfuly received.