The old FMEA scoring method could mathematically rank a minor cosmetic defect above a failure that hurts someone. Why the industry replaced Risk Priority Number with Action Priority in 2019, and how FMEA differs from reactive root cause analysis.
The old FMEA scoring method could mathematically rank a minor
cosmetic defect above a failure that hurts someone — multiply three
1-to-10 scales together and the math doesn’t know the difference
between “annoying” and “dangerous” when the numbers happen to line up.
That’s exactly why the industry replaced it in 2019.
Failure Mode and Effects Analysis (FMEA) is a proactive risk-analysis
method, originating with reliability engineers in the late 1950s for
military applications. It works by systematically walking through a
design or process, asking three questions for each potential failure:
how severe would it be, how likely is it to occur, and how likely is it
to be detected before it reaches the customer.
That makes FMEA fundamentally different from root cause analysis or
A3 problem solving — those tools react to a failure that’s already
happened. FMEA tries to find the failure before it ever occurs.
The traditional approach multiplied Severity, Occurrence, and
Detection ratings — each on a 1-to-10 scale — into a single Risk
Priority Number (RPN). The problem: multiplying ordinal scales together
can produce a lower-severity, high-occurrence failure with the same or
higher RPN than a high-severity, low-occurrence one. A team ranking
purely by RPN could end up prioritizing the wrong risk.
| Old RPN method | AIAG-VDA Action Priority (2019) | |
|---|---|---|
| Calculation | Severity × Occurrence × Detection | Severity, Occurrence, and Detection combined through a structured decision table, not simple multiplication |
| Output | A single number to rank against a cutoff | High / Medium / Low action priority rating |
| Weakness addressed | — | Prevents high-severity, low-occurrence risks from being mathematically outranked by lower-severity, high-occurrence ones |
In 2019, AIAG (the Automotive Industry Action Group) and VDA
(Germany’s automotive industry association) jointly published a
harmonized FMEA handbook that replaced the old RPN calculation with this
Action Priority approach — ending years of U.S. and European automakers
requiring slightly different FMEA formats from the same suppliers.
A supplier still running the old RPN-based FMEA format when a
customer expects the AIAG-VDA Action Priority format isn’t just
behind on paperwork style — the underlying risk logic is different
enough that ratings don’t translate cleanly between the two systems.
Given South Carolina’s dense automotive supplier base, confirming which
FMEA format a specific customer requires before starting the analysis
saves a costly rework cycle later.
FMEA itself isn’t a standalone course in SCMEP’s current catalog —
it’s one of the automotive core tools that builds on the quality
fundamentals in our ISO 9001:2015
Overview. As a NIST Manufacturing Extension
Partnership affiliate serving South Carolina manufacturers since
1989, our focus is helping teams run FMEA as a genuine
cross-functional risk exercise, not a form filled out by one engineer
alone.
If your team is building or updating an FMEA process, you can
browse the Quality and Inspection
training catalog or email the training team.
FMEA identifies where a failure could happen; poka-yoke is one of the ways to make it physically impossible. See our related guide on poka-yoke error-proofing for Shigeo Shingo’s three error-proofing methods.
Failure Mode and Effects Analysis is a proactive risk-analysis method that systematically evaluates potential failures in a design or process by rating their severity, likelihood of occurrence, and likelihood of detection before they reach the customer.
Multiplying Severity, Occurrence, and Detection ratings together could mathematically rank a lower-severity, high-occurrence failure above a high-severity, low-occurrence one, potentially misdirecting a team’s risk priorities.
In 2019, AIAG and VDA jointly published a harmonized FMEA handbook that replaced RPN with an Action Priority (AP) rating — High, Medium, or Low — determined through a structured decision table rather than simple multiplication.
FMEA is proactive — it tries to identify potential failures before they happen. Root cause analysis and A3 problem solving are reactive — they investigate a failure that has already occurred.
