Question 1

What is FMEA Severity rating?

Accepted Answer

FMEA Severity (S) is a numerical rating from 1 to 10 that evaluates the seriousness of a potential failure mode's effect. A rating of 1 indicates no discernible effect, while 10 indicates a hazardous effect affecting safety. Ratings of 9 or 10 require immediate priority attention regardless of other factors, per AIAG VDA Handbook standards.

Question 2

How is RPN calculated in FMEA?

Accepted Answer

Risk Priority Number (RPN) is calculated by multiplying Severity (S) x Occurrence (O) x Detection (D), yielding a value from 1 to 1,000. The AIAG VDA 4th Edition (2019) recommends using Action Priority (AP) instead of RPN, because AP better prioritizes risk by weighting Severity and Occurrence over Detection.

Question 3

What is the difference between AIAG and VDA FMEA ratings?

Accepted Answer

The AIAG VDA FMEA Handbook (4th Edition, 2019) is a harmonized standard replacing the separate AIAG FMEA 4th Edition and VDA Volume 4. Key changes include: Action Priority (AP) tables replacing traditional RPN thresholds, updated harmonized SOD criteria, and a new 7-step FMEA methodology. All tables on fmearatings.com reflect the current AIAG VDA standard.

Question 4

What are the standard FMEA Severity, Occurrence, and Detection (SOD) ratings?

Accepted Answer

FMEA ratings use a scale from 1 to 10. Severity measures failure impact (1 = no effect, 10 = safety risk), Occurrence ranks failure probability, and Detection assesses how likely controls will find the failure before reaching the customer.

Question 5

How do I use the FMEA Severity Table 1-10 according to AIAG & VDA standards?

Accepted Answer

The AIAG VDA FMEA Handbook provides updated criteria for the 1-10 scale. A rating of 9 or 10 always indicates a potential safety or regulatory non-compliance issue. The focus has shifted from calculating RPN to understanding the functional impact of each failure mode.

Question 6

What is the difference between RPN and Action Priority (AP) in FMEA?

Accepted Answer

RPN is calculated by multiplying Severity x Occurrence x Detection. The new Action Priority (AP) system uses a logic-based table to categorize risk as High, Medium, or Low. AP is preferred over RPN because it prioritizes the combined impact of severity and occurrence rather than just the product of three numbers.

Question 7

Where can I find a PFMEA and DFMEA Occurrence Table?

Accepted Answer

Comprehensive PFMEA and DFMEA occurrence tables are available on fmearatings.com. These tables help assign a ranking from 1 (nearly impossible) to 10 (persistent failure) based on historical data, preventive controls, and predicted failure rates.

Question 8

Why is a Detection ranking of 10 critical in a risk assessment?

Accepted Answer

A Detection ranking of 10 means there is no control in place to detect the failure mode. Even if occurrence is low, a detection ranking of 10 often triggers an immediate need for improved inspection methods or automated sensors to protect the end-user.

S	Effect	Impact to Your Plant	Impact to Ship-to Plant (when known)	Impact to End User (when known)
10	High	Failure may result in health and/or safety risk for the manufacturing or assembly worker	Failure may result in health and/or safety risk for the manufacturing or assembly worker	Affects safe operation of the vehicle and/or other vehicles, the health of driver or passenger(s) or road users or pedestrians
9	High	Failure may result in in-plant regulatory noncompliance	Failure may result in in-plant regulatory noncompliance	Noncompliance with regulations
8	Moderately high	100% of production run affected may have to be scrapped	Line shutdown greater than full production shift; stop shipment possible, field repair or replacement required (Assembly to End User) other than for regulatory noncompliance.	Loss of primary vehicle function necessary for normal driving during expected service life
7	Moderately high	Product may have to be sorted and a portion (less than 100%) scrapped; deviation from primary process, decreased line speed or added manpower	Line shutdown from 1 hour up to full production shift; stop shipment possible, field repair or replacement required (Assembly to End User) other than for regulatory noncompliance	Degradation of primary vehicle function necessary for normal driving during expected service life
6	Moderately low	100% of production run may have to be reworked off line	Line shutdown up to one hour	Loss of secondary vehicle function
5	Moderately low	A portion of the production run may have to be reworked off line and accepted	Less than 100% of product affected; strong possibility for additional defective product; sort required; no line shutdown	Degradation of secondary vehicle function
4	Low	100% of production run may have to be reworked in station before it is processed	Defective product triggers significant reaction plan; additional defective products not likely, sort not required	Very objectionable appearance, sound, vibration, harshness, or haptics
3	Low	A portion of the production run may have to be reworked in station before it is processed	Defective product triggers minor reaction plan; additional defective products not likely, sort not required	Moderately objectionable appearance, sound, vibration, harshness, or haptics
2	Low	Slight inconvenience to process, operation, or operator	Defective product triggers no reaction plan; additional defective products not likely, requires feedback to supplier	Slightly objectionable appearance, sound, vibration, harshness, or haptics
1	Very low	No discernible effect	No discernible effect or no effect	No discernible effect

O	Prediction of Failure Cause Occurring	Incidents per 1000 items/vehicles	Time Based Failure Cause Prediction	Type of Control	Prevention Controls
10	Extremely high	≥ 100 per thousand, ≥ 1 in 10	Every time	None	No prevention controls.
9	Very high	50 per thousand, 1 in 20	Almost every time	Behavioral	Prevention controls will have little effect in preventing failure cause.
8	Very high	20 per thousand, 1 in 50	More than once per shift	Behavioral	Prevention controls will have little effect in preventing failure cause.
7	High	10 per thousand, 1 in 100	More than once per day	Behavioral or Technical	Prevention controls somewhat effective in preventing failure cause.
6	High	2 per thousand, 1 in 500	More than once per week	Behavioral or Technical	Prevention controls somewhat effective in preventing failure cause.
5	Moderate	0.5 per thousand, 1 in 2,000	More than once per month	Behavioral or Technical	Prevention controls are effective in preventing failure cause.
4	Moderate	0.1 per thousand, 1 in 10,000	More than once per year	Behavioral or Technical	Prevention controls are effective in preventing failure cause.
3	Low	0.01 per thousand, 1 in 100,000	Once per year	Best Practices: Behavioral or Technical	Prevention controls are highly effective in preventing failure cause.
2	Very low	≤ 0.001 per thousand, 1 in 1,000,000	Less than once per year	Best Practices: Behavioral or Technical	Prevention controls are highly effective in preventing failure cause.
1	Extremely low	Failure is eliminated through prevention control	Never	Technical	Prevention controls are extremely effective in preventing failure cause from occurring due to design (e.g. part geometry) or process (e.g. fixture or tooling design).

D	Ability to Detect	Detection Method Maturity	Opportunity for Detection
10	Very low	No testing or inspection method has been established or is known	The failure mode will not or cannot be detected
9	Very low	It is unlikely that the testing or inspection method will detect the failure mode	The failure mode is not easily detected through random or sporadic audits.
8	Low	Test or inspection method has not been proven to be effective and reliable (e.g. plant has little or no experience with method, gauge R&R results marginal on comparable process or this application, etc.)	Human inspection (visual, tactile, audible), or use of manual gauging (attribute or variable) that should detect the failure mode or failure cause
7	Low	Test or inspection method has not been proven to be effective and reliable (e.g. plant has little or no experience with method, gauge R&R results marginal on comparable process or this application, etc.)	Machine-based detection (automated or semi-automated with notification by light, buzzer, etc.), or use of inspection equipment such as coordinate measuring machine that should detect failure mode or failure cause
6	Moderate	Test or inspection method has been proven to be effective and reliable (e.g. plant has experience with method, gauge R&R results acceptable on comparable process or this application, etc.)	Human inspection (visual, tactile, audible), or use of manual gauging (attribute or variable) that will detect the failure mode or failure cause (including product sample checks)
5	Moderate	Test or inspection method has been proven to be effective and reliable (e.g. plant has experience with method, gauge R&R results acceptable on comparable process or this application, etc.)	Machine-based detection (semi-automated with notification by light, buzzer, etc.), or use of inspection equipment such as coordinate measuring machine that will detect failure mode or failure cause (including product sample checks)
4	High	System has been proven to be effective and reliable (e.g. plant has experience with method on identical process or this application), gauge R&R results are acceptable, etc.	Machine-based detection method that will detect failure mode downstream, prevent further processing or system will identify the product as discrepant and allow it to automatically move forward in the process until the designated reject unload area. Discrepant product will be controlled by a robust system that will prevent outflow of the product from the facility
3	High	System has been proven to be effective and reliable (e.g. plant has experience with method on identical process or this application), gauge R&R results are acceptable, etc.	Machine-based detection method that will detect failure mode in-station, prevent further processing or system will identify the product as discrepant and allow it to automatically move forward in the process until the designated reject unload area. Discrepant product will be controlled by a robust system that will prevent outflow of the product from the facility
2	Very high	System has been proven to be effective and reliable (e.g. plant has experience with method on identical process or this application), gauge R&R results are acceptable, etc.	Machine-based detection that will detect the cause and prevent the failure mode (discrepant part) from being produced
1	Very high	Failure mode cannot be physically produced as-designed or processed	Detection methods proven to always detect the failure mode or failure cause

PFMEA Rating Tables

PFMEA vs DFMEA — Key Differences

PFMEA Severity (S) Rating Table

PFMEA Occurrence (O) Rating Table

PFMEA Detection (D) Rating Table