Electronic Troubleshooting#
Ben Manning, Purdue University
Last Modified: 2026-01-06
Effective troubleshooting is essential in reverse engineering, whether analyzing an unknown circuit or diagnosing a system’s unexpected behavior. The 5 Whys method provides a structured approach to uncover the root causes of issues by repeatedly asking “Why?” This technique prevents mere symptom treatment and leads to more effective problem resolution.
Applying the 5 Whys to Reverse Engineering#
The 5 Whys method can be used to diagnose failures in reverse engineering processes by following these steps:
1. Identify the Problem#
Clearly define the issue. Example: “The microcontroller-based system under analysis does not respond to inputs.”
2. Ask “Why?” Repeatedly#
Follow a logical sequence of questioning:
Why is the system not responding? Because the microcontroller is not executing the expected code.
Why is the microcontroller not executing the expected code? Because it is not receiving power.
Why is the microcontroller not receiving power? Because the voltage regulator is not supplying the correct output.
Why is the voltage regulator failing? Because it is not receiving the expected input voltage.
Why is the input voltage incorrect? Because there is a broken trace on the PCB, disrupting power delivery.
By reaching the fifth Why, we have identified the root cause: a broken PCB trace. Rather than replacing components, we now understand the need to inspect and repair PCB traces to restore functionality.
Breadboard Troubleshooting in Reverse Engineering#
Breadboards are essential tools for prototyping and reverse engineering circuits, but they can introduce their own issues. Common problems include loose connections, misplaced components, or unintended shorts. The 5 Whys method can also be applied to troubleshoot breadboard circuits:
Why is the circuit not functioning as expected? Because the microcontroller is not receiving power.
Why is the microcontroller not receiving power? Because the power rails are not properly connected.
Why are the power rails not properly connected? Because the jumper wires are incorrectly placed.
Why were the jumper wires placed incorrectly? Because the schematic was misinterpreted.
Why was the schematic misinterpreted? Because the labeling on the schematic was unclear.
By applying the 5 Whys method, we can see that an unclear labeling issue led to a misinterpretation of the schematic and improper wiring, rather than simply assuming a faulty component.
Advantages of the 5 Whys Method in Reverse Engineering#
Prevents misdiagnosing issues by identifying the true cause.
Helps in mapping unknown circuits and understanding design flaws.
Encourages logical thinking when reconstructing how a system was designed.
Can be supplemented with tools like logic analyzers, oscilloscopes, and schematic tracing for enhanced debugging.
Useful in diagnosing both PCB and breadboard-related issues in reverse engineering projects.
Conclusion#
The 5 Whys technique is a valuable tool for troubleshooting in reverse engineering. By methodically questioning the cause of failures, engineers can go beyond surface-level issues and gain a deeper understanding of system design. This approach enhances diagnostic accuracy, reduces repeated failures, and strengthens problem-solving skills in electronics and hardware analysis.