Root Cause Analysis: 5 Whys & Fishbone Template
A structured investigation log that combines the Fishbone (Ishikawa) diagram with the 5-Whys technique to identify root causes of equipment failures and document corrective actions. Use this form whenever a critical asset experiences an unplanned outage, recurring fault, or quality deviation.
The 5-Whys and Fishbone (Ishikawa) method is a structured root cause analysis (RCA) technique used to uncover the underlying cause of equipment failure — not just the symptom. This template guides a cross-functional team through cause categorization (Machine, Material, Method, Manpower, Measurement, Environment), iterative questioning, and corrective action assignment. Use it to eliminate repeat failures, reduce downtime, and strengthen your preventive maintenance program.
- Ensure the failed equipment is locked out and de-energized before any hands-on investigation begins. Verify zero energy state.
- All team members must wear appropriate PPE: safety glasses, steel-toed boots, and gloves when handling components or debris.
- Assemble a cross-functional team: operator, maintenance technician, supervisor, and quality/process representative.
- Gather available data: failure timestamp, operating parameters, maintenance history, operator notes, and any trend logs.
Fishbone Cause Mapping & 5-Whys Investigation Matrix
| Category | Probable Cause | 5-Whys Drill-Down (Why? → Why? → Why? → Why? → Why?) | Root Cause Found | Status (P/F) |
|---|---|---|---|---|
| Machine | Worn bearing / misalignment | Why1: Excessive vibration → Why2: Lubrication starvation → Why3: Incorrect grease type → Why4: No spec on PM card → Why5: PM procedure not reviewed | _________________________ | [ ] P [ ] F |
| Material | Raw material variability | Why1: Hardness outside spec → Why2: Supplier lot change → Why3: Incoming inspection not performed → Why4: No gauge available → Why5: Budget for gauge not approved | _________________________ | [ ] P [ ] F |
| Method | Improper startup sequence | Why1: Warm-up skipped → Why2: Operator unaware of new procedure → Why3: Shift handoff failed → Why4: No written SOP → Why5: SOP not created after last modification | _________________________ | [ ] P [ ] F |
| Manpower | Inadequate training on new PLC | Why1: Technician could not navigate HMI → Why2: Training session cancelled → Why3: No trainer available → Why4: OEM training budget frozen → Why5: No training priority assigned | _________________________ | [ ] P [ ] F |
| Measurement | Pressure gauge out of calibration | Why1: Readings drifted by 12% → Why2: Calibration overdue by 4 months → Why3: No calibration tracking system → Why4: Relied on operator memory → Why5: No formal calibration program | _________________________ | [ ] P [ ] F |
| Environment | Ambient temperature spike | Why1: Compressor room temp reached 42°C → Why2: Exhaust fan failed → Why3: No PM on ventilation → Why4: Fan not on asset list → Why5: Asset register incomplete | _________________________ | [ ] P [ ] F |
* For each probable cause, ask "Why?" five times until the true root cause is exposed. Record each drill-down in the column above.
Corrective & Preventative Action Plan
| Root Cause Statement | Corrective Action | Assigned To | Due Date | WO # | Status |
|---|---|---|---|---|---|
| _________________________ | _________________________ | _________________ | ___/___/_____ | _______ | [ ] Open [ ] Closed |
| _________________________ | _________________________ | _________________ | ___/___/_____ | _______ | [ ] Open [ ] Closed |
| _________________________ | _________________________ | _________________ | ___/___/_____ | _______ | [ ] Open [ ] Closed |
By signing below, the investigation team verifies that the root cause analysis has been completed according to the 5-Whys and Fishbone methodology, all contributing causes have been documented, and corrective actions are assigned and tracked.