When a maintenance guide lists several possible field-replaceable units (FRUs) that might fix a fault, what is the correct next step after powering down the system?

Introduction / Context:
Field-replaceable unit (FRU) methodology aims to minimize downtime and cost while restoring function. Proper replacement order and verification reduce the risk of misdiagnosis and new faults introduced during repair.

Given Data / Assumptions:

• A validated maintenance document lists multiple possible FRUs.
• The device has been safely powered off and ESD precautions are in place.
• Goal: resolve the fault efficiently and traceably.

Concept / Approach:

Best practice is controlled substitution: replace only one FRU at a time following the manufacturer’s recommended sequence. After each swap, retest to confirm whether the fault is cleared. This isolates the root cause and prevents unnecessary replacement of serviceable parts.

Step-by-Step Solution:

Verification / Alternative check:

Most OEM service manuals and ITIL-style procedures specify single-variable changes to ensure clear cause-effect attribution and maintain proper parts control.

Why Other Options Are Wrong:

• Replace all FRUs at once: wasteful and obscures the actual root cause.
• Always replace the system board first: unnecessarily invasive and expensive; follow documented order.
• Assume software is most likely: may delay hardware resolution; diagnostics already pointed to FRUs.
• None of the above: incorrect because controlled, one-at-a-time FRU replacement is correct.

Common Pitfalls:

• Skipping retest after each change, which complicates root-cause analysis.
• Failing to re-image or re-seat connections properly after replacement.

Final Answer:

Replace the indicated parts one at a time in the recommended sequence until the issue is resolved; return any unused FRUs to stock.