Six-Steps For Troubleshooting Electrical Failures
The Six-Step Troubleshooting Method
Diagnosing electrical related failures can be incredibly challenging on modern vehicles because of both the complexity of their systems and circuits and the sheer volume of wiring, controllers and other components that are installed in them. Factor in CAN bus and other Data networks and it can get confusing to even know where to start.
Using a methodical approach can greatly reduce the time you spend identifying a root cause and prevent misdiagnosis, a true win-win. In this article, I will share with you a six-step troubleshooting method that has greatly helped me properly diagnose electrical issues quicker and more accurately.
Step 1. Verify the Problem
Distinguish legitimate failures from normal operation/customer misunderstandings. The owner’s manual will describe the normal operation of most systems. Of course, the manual isn’t always available and most owners haven’t read them. In some cases, customers lack of knowledge may lead to misinterpreting a new system or function as a failure. So, the radio may be programmed to stay on after the car ignition is switched off. It should turn off after a predetermined amount of time but the customer thinks something is wrong. Always refer to the Service Manuals in Direct-Hit for information when trying to discern between normal and abnormal operation.
Step 2. Determine Related Symptoms (Find Common Ground)
Observe related systems or functions that may exhibit symptoms. Many systems share common elements such as fuses and grounds. Identifying logical common points can minimize inspection points. For example, a dull headlamp and an inoperative turn signal may share a ground point. To find out what electrical problems all share a common link, the best place to start is the wiring diagram or Electrical Troubleshooting Manual (ETM).
Step 3. Isolate the Problem
Draw a simplified sketch of the suspect circuit and identify critical components, connectors and construction type (IE. Series, Parallel, Series-Parallel).
Use the Split-Half technique. This is a technique that reduces the number of measurements needed to isolate the faulty wire or component. Suppose you have an open circuit in the 5-volt supply between a control module and a sensor and there are 5 connectors in the circuit. A. B, C, D, and E. The next measurement point should be about in the middle of the circuit, C. This will let us know which half of the circuit to test next. Between the mid-point and the control unit or between the mid-point and the component.
Step 4. Identify the Cause
Open Circuits: Voltage not making it to a component or voltage on a normally grounded circuit. This could indicate broken wires, open or corroded connections, broken splices, etc.
Short Circuits: These will be blowing fuses or are control circuits that are always grounded or even potentially have voltage all the time.
High Resistance/Voltage Drop: Only 6 of the available 12 Volts is making it to a headlamp or to a slow running cooling fan.
Step 5. Repair the Problem
Whatever repair is required, it should be done correctly. Some manufacturers have specific requirements to maintain the resistance of the circuit. For instance, some manufacturers want heat shrink crimp or butt connectors and they should be crimped by a certain tool to crimp it with the right amount of force.
Correct the pin fit (sliding resistance) by proper replacement techniques. Fixing corrosion problems at the control module or sensor connectors, splices should all get done to prevent a costly comeback.
Repair or replace the wire using the twist, solder and shrink sleeve methods.
Step 6. Verify the Operation
Thoroughly inspect that the repair has been accurately performed and the electrical failure will not return. This step is critical in ensuring customer satisfaction through measurements. Does the component or system return to normal operation? For engine controls, does the component monitor run and pass?
Putting a Methodical Approach to Use
By following these steps or a similar process you can greatly reduce the time you spend identifying a root cause and feel more confident in your diagnosis. Don’t be afraid to keep notes or steps written down somewhere on a piece of paper or on your phone to reference as needed.