What Is an FMEA Table and How Do You Use It Correctly?

Failure Mode and Effects Analysis (FMEA) is a structured method for identifying potential failures in a product or process before they occur. The FMEA table is the core working document where the analysis is recorded. This article explains what it is, how to build one, and how to interpret it correctly — whether you follow the legacy AIAG format or the newer AIAG & VDA approach.

What It Is

An FMEA table is a spreadsheet-style form that captures, for each potential failure mode:

• What could go wrong (failure mode)
• What effect it would have (effect of failure)
• What causes it (potential cause)
• What controls currently exist (prevention and detection)
• A risk ranking (either RPN or Action Priority)

The table forces a cross-functional team to think systematically about risk — not just react to problems after they appear.

How It Works: Formula and Steps

### Legacy Method (AIAG FMEA-4, historical)

The classic FMEA table uses three rating scales from 1 to 10:

• S — Severity (how serious the effect is)
• O — Occurrence (how likely the cause is to happen)
• D — Detection (how likely current controls will catch it; 10 = almost impossible to detect)

RPN = S × O × D

Teams typically set a threshold (e.g., RPN > 100) to decide which items need action. However, this threshold approach has a known weakness: a high RPN can hide a single critical factor. For example, S = 10, O = 2, D = 2 gives RPN = 40 — below threshold, yet the severity is maximum.

### New Method (AIAG & VDA FMEA Handbook, 1st Ed., 2019)

The 2019 AIAG & VDA handbook replaces the RPN threshold with Action Priority (AP). Instead of multiplying three numbers, the team assigns each failure mode an AP level by looking up the combination of S, O, and D in a predefined table:

• H (High) — action is required
• M (Medium) — action should be taken
• L (Low) — action may be considered

The AP table is not a simple product — it prioritizes severity first. For instance, an S = 10 combination can never be Low, regardless of O and D values. This corrects the legacy blind spot.

### Standard Steps to Fill the Table

1. Define the system, subsystem, or process under analysis.
2. List every function or requirement.
3. For each function, list potential failure modes.
4. For each failure mode, describe the effect, cause, and current controls.
5. Rate S, O, and D using the scale definitions in your chosen standard.
6. Compute RPN (legacy) or look up AP (AIAG & VDA).
7. Assign actions for high-risk items, then re-rate after actions are implemented.

A Worked Illustrative Example

Example data (illustrative only) — not from any real factory.

Consider a process step: "Drill mounting holes in a bracket."

Failure Mode | Effect | S | Cause | O | Current Control | D | RPN (legacy) | AP (AIAG-VDA)

• Hole position off-center | Bracket fails to align in assembly | 8 | Worn drill bushing | 4 | 100% inspection by operator | 6 | 8×4×6 = 192 | H
• Hole diameter too small | Bolt cannot pass through | 7 | Drill bit worn | 3 | No detection control | 8 | 7×3×8 = 168 | M

In the legacy view, both items exceed a typical threshold of 100, so both need action. Under AIAG & VDA, the first item is High priority (because severity is 8 and detection is poor), while the second is Medium. The recommended action for the first item might be "Replace bushing on a preventive maintenance schedule and add a go/no-go gauge."

Common Pitfalls

• Mixing versions. Do not use the AIAG & VDA AP table but then apply a legacy RPN threshold. They are different risk-ranking philosophies.
• Rating inflation. Teams often rate everything as 8–10 to "be safe." This destroys the discriminating power of the table.
• Forgetting prevention controls. The new handbook distinguishes between prevention controls (reduce O) and detection controls (reduce D). Listing only detection controls is a common error.
• One-person FMEA. A table filled by a single engineer misses cross-functional insight. Always involve design, manufacturing, and quality.

Closing

A well-constructed FMEA table turns subjective worry into a ranked, documented action plan. Whether you use the legacy RPN or the newer AIAG & VDA Action Priority, the key is consistency and team discipline. To get started quickly, you can use a free, structured FMEA template at 6SQ's FMEA tool — it supports both the legacy and AIAG & VDA rating logic so you can build your table correctly from day one.