Testing Ground and Low Reference Circuits: Notes

The testing of ground and low reference circuits can be performed in multiple ways using multiple tools. Ground circuits may be tested in the following ways:

• Measuring resistance with a DMM
• Testing continuity with a test lamp
• Measuring voltage drop with a DMM

Each method of testing a ground or low reference circuit requires attention and understanding of the tools and results to ensure misdiagnosis does not occur based on the results:

• A DMM requires a more specific set of conditions on the vehicle when testing, but will accurately measure resistance. A DMM may not identify a ground or low reference circuit that maintains continuity, but is damaged and has compromised load carrying capability.
• Testing a ground or low reference circuit with a test lamp is a good way to quickly determine continuity, but may not identify all instances of excessive resistance.
• Measuring voltage drop with a DMM is a very accurate way to test a ground or low reference circuit, but requires the most time and effort to access components and ground locations.