1997 Acura CL ABS light on

After the technician changed the router anf the pad (?). The steering wheel did not shake any more when I put on the brake pedal. But I have other problem that THE ABS LIGHT STAYED ON DURING THE CAR WAS MOVING.
I had the technician check the problem. He said he didnot cause the ABS light on. While changing the riuter/pad.
Could you please tell me what cause the ABS light on like that?
Should I take my car to the dealer to diagnose /fix the problem (costs me lots of money)? Or should I take my car to a foreing car garage to fix the problem?

your help will be appreciated very much! Please answer my question ASAP cuz the winter will come soon.