Abs light on, per firestone "short in abs system "

Help how do I trouble shoot this, abs light is on. According to firestone there is a short in the abs system.
any help would be much appreciated!
thanks.

take it to another shop and see what they say

If you paid for a scan and they gave you that generic answer to the problem, you got ripped off. Typically, most ABS issues are caused by an open circuit to a wheel speed sensor, not a short. A proper scan should give you a report indicating which wheel is the culprit.