Quality managementReading time 13 min

FMEA Action Priority: What Changed After RPN

Multiplying severity, occurrence and detection can hide a severe failure behind a low RPN. The newer Action Priority approach changes how teams decide what to address first—and what evidence to record.

01Severity, occurrence and detection

Item	Asks	A score of 1	A score of 10
Severity S	How serious the consequence is when the failure occurs	Almost no effect	Affects safety or violates regulation, without warning
Occurrence O	How often this cause happens	Practically impossible	Very high, happening continuously
Detection D	How easily current controls catch it	Almost certain to be caught	Cannot be detected, or is never checked

For detection, a higher rating means the control is less likely to catch the failure.

02Why RPN can mislead

Traditional RPN multiplies severity, occurrence and detection into one score. Different risk profiles can produce the same result, so a single threshold may hide a severe failure mode. Action Priority evaluates the three ratings in a defined order instead of treating every product as equivalent.

The same product, different meaning. 9×2×2 = 36 and 2×9×2 = 36 score identically, but the first is a safety issue and the second a common cosmetic flaw.
It is discontinuous. Of 1000 possible products only 120 are distinct values, so a great many items tie.
It invites gaming. To get under the threshold, change D from 7 to 6 and it passes, which changes the number, not the risk.

03Using Action Priority

The AIAG-VDA method introduced Action Priority in place of a simple RPN threshold. A priority table considers severity first, then occurrence and detection, producing a high, medium or low action priority.

Situation	AP	Meaning
S 9-10 with O 4-10	H	Action must be taken, or a reason given for not taking it
S 9-10 with O 2-3 and high D	H	As above
S 7-8 with O 6-10	H	High priority
Mid-range combinations	M	Action should be taken, or the rationale recorded
Low S with low O	L	Action may be omitted, but record it

Action Priority comes from a defined table; it is not another product of three scores.

High priority does not mean the team must somehow force the result to low. It means the risk needs an action or a documented reason for not taking one. The aim is a defensible decision, not a better-looking score.

04The seven-step approach

Planning and preparation. Define the scope, project boundaries and participants (the 5T: intent, timing, team, task, tool).
Structure analysis. Break the system into three levels: system, subsystem, and component or process step.
Function analysis. What each level has to do, expressed so it can be measured.
Failure analysis. The chain of failure effect, failure mode and failure cause.
Risk analysis. Rate S, O and D and look up the AP.
Optimisation. Propose actions for H and M items, assign owners and dates, and re-rate.
Documenting results. Communication and records, internal and external.

05Keep FMEA current

FMEA should change when the process changes. A complaint, new failure mode, revised control or updated drawing is a reason to review it with the people who run and inspect the process.

a customer complaint or a serious internal defect (D7 of an 8D should go back and change the FMEA)
a design change, material change or supplier change
a change of process parameters or equipment
a clear gap between the actual early-production defect rate and the O originally rated