Sometimes a meter will show grounded. Like the starter circuit when the key is turned to the start position. "High" resistance is bad and "low" is good or better. Not all wires are fused. Some are protected by the fusable link to prevent a meltdown in case of a short and by the time you know, it's too late. A grounded wire and resistance are two different things. Resistance is the how much effort it takes for electrical current to flow.

If it's only with the key turned to "on", it's a matter of isolating it. Look at any circuit that is powered then..like the alternator/harness, heater switch, turn signal, etc...