What is the typical source for reading electrical fault codes on an aircraft?

• A. Visual inspection of wiring harnesses
• B. From the fault memory or maintenance computer
• C. Interpreting the flight crew's logs manually
• D. Reading from the air data computer

Answer: (B)

Fault codes come from the aircraft’s fault memory in the maintenance computer. When electrical systems detect a fault, they generate a diagnostic trouble code and store it in that centralized memory. A technician then retrieves these codes with a maintenance laptop or portable tester connected to the aircraft, using the fault memory as the single source of truth. This approach lets you quickly identify the affected subsystem or component and guide the troubleshooting steps. Visual inspection can uncover obvious damage but doesn’t provide standardized codes, and manually interpreting flight crew logs isn’t how these diagnostics are captured. The air data computer processes sensor data and may report its own faults, but the official fault codes are stored in the fault memory accessed via the maintenance interface.