About Shared Current Paths, the Vehicle Base System
It is smart troubleshooting to do a complete shared current path base system tests on every vehicle exhibiting drive ability symptoms that cannot be pinpointed with scan testing and code retrieval.
If a part, or a connection between the parts, of the base system is not performing as engineered, sometimes the results can be as severe as a no crank-no start, or rather subtle.
A base system that has lost its design integrity has been known to cause: drivability problems; intermittent electrical / electronic, including digital dash, problems; engine idling (no load) and running (load) problems; flickering lights; and other problems.
You need to verify a sound base system and all of its conductors, connectors, connections, and contacts before you attempt to fix anything.
An increase in current flow across a base system shared-ground connection can cause a voltage drop at a point in the ground return that could result in voltage being reduced or denied to some component totally unrelated to the load that is seeking ground.
If a particular splice, connection, or section of the wiring in the base-system shared-ground return developed excessive resistance, the current has many other paths, not contained-in-wire, where it can seek its ground back to the battery’s negative (-) terminal. This current can play havoc in an electrical or electronic system when it seeks ground through a path that was not engineered for its use.
If you jump into testing an individual circuit before testing the base system, you may never find what could have been the cause of the complaint, because the symptom may be due to a problem in the base-system shared-voltage feed or ground return current paths.
Without verifying the base system first, you could spend a lot of time troubleshooting an individual circuit, looking for something that is not there, changing parts, and fixing nothing.
If you skip base-system testing and go right on to individual circuit testing, some voltage drops that cause symptoms of complaint may never be found.
Individual circuit testing should never be performed until after all base-system testing has been completed, and all excessive voltage drops in the base system have been reduced to an acceptable standard.
When you are confident that the base system is working as engineered, and that all of its conductors, connectors, connections, and contacts have acceptable voltage drops; then, and only then, should you continue with any diagnosis of any individual circuit.
You will find, in some cases, that after testing and repairing the base system, the problem that the vehicle came in with will have been repaired.
If you are unfamiliar with the “base system” of a vehicle’s electrical/electronic system, my book entitled: “Understanding and Troubleshooting Vehicle Voltage Drop”, starting on page 37: “Understanding Shared Current Paths, The Vehicle “Base System” explains this in detail.
You can purchase my book through the “Shopping Cart” page.