Yes at 1.5 ohms of resistance measured at 7 way connector that’s telling you there is an issue with one or more of the magnets and or wiring to the magnets
Should read about 12.5 to 13.5 ohms in a dual axle trailer. Your ohm meter is more than capable of making that reading. No “special” tool required...
The magnets weak point is where the molded wire comes out of the brake magnet armature and is a known issue. This is why it’s good to look at and physically check wire harness condition on each magnet when you remove hubs annually for inspect and grease repack