Depending on production batch. You might get a slightly different reading on you glow plugs. Usually though it will be 1-2 ohms. You are on the lookout for one that has no resitance. It has burnt open. Or burnt out.

This will be the typical failure mode. There are more complex tests if the need is there. Yet if finding the burned plugor plugs and replacing it or them gets you underway is usually good enough.