The Milliohm meter offers the ability to measure resistance between phases of motor generator units when dealing with related fault codes. A Digital Multi meter cannot measure the very small resistance values required to do this or verify good electrical connections.
The Milliohm meter is designed to read very small values of resistance. In order to get a precise reading the milliohm meter utilises a 4-wire resistance measurement in which two of the wires pass the current through the circuit while the other two wires make the delta (difference between two points) voltage measurement.
When you are dealing in milliohms the testing temperature of the windings and equipment becomes incredibly important, (as temperature increases so does resistance). For example: Toyota’s service information states that all testing should be performed at 20°C, failure to do so may give inaccurate readings and consequently incorrect diagnosis.