In fault isolation, what comes after isolating the symptom?

• A. Verify power sources.
• B. Check fuse/bus status.
• C. Follow QRH steps.
• D. Test circuits.

Answer: (D)

After isolating the symptom, you move to testing the circuits involved to confirm the fault path and locate the exact fault. By checking continuity, resistance, voltage, current, and insulation in the affected wiring and components, you gather concrete evidence about where the fault lies—whether it’s a broken conductor, a short, or a failed device. This step turns the symptom into a specific fault location you can repair. Verifying power sources and following QRH steps are relevant in handling abnormal conditions, but they don’t pinpoint the fault as directly as circuit testing does. Testing circuits provides the measurable data needed to identify the exact faulty element and guide the repair.