Root Cause Analysis (RCA) Tool

Overview

Effective corrective action (Clause 10.2) requires finding the root cause, not just fixing the symptom. This tool provides two common methods.

Method 1: The 5 Whys

Ask “Why?” five times to drill down to the root cause.

• Problem: The vehicle wouldn’t start.
  1. Why? The battery is dead.
  2. Why? The alternator is not functioning.
  3. Why? The alternator belt has broken.
  4. Why? The belt was well beyond its useful service life and not replaced.
  5. Why? The vehicle was not maintained according to the recommended service schedule. (ROOT CAUSE)

Method 2: Fishbone Diagram (Ishikawa)

Categorize potential causes into 6 Ms:

1. Man (People): Training, fatigue, competence.
2. Machine (Equipment): Maintenance, calibration, capability.
3. Material: Raw materials, consumables.
4. Method: Procedures, instructions, standards.
5. Measurement: Gauges, accuracy, bias.
6. Mother Nature (Environment): Temperature, humidity, lighting.