Update: I stopped using the multimeter's auto range on connector pins and my readings finally match
Everyone at my shop swears by auto range for quick pin checks, but I went back to locking the range manually on a 737 harness job at Boeing Field and found two pins that auto range had been reading as open. It was scanning past the real value because of the tiny signal, and a fixed range caught it right away. Anyone else run into that, or am I just slow with the meter?