Severity in FMEA (AIAG-VDA) | Explained with Examples

In today’s automotive manufacturing industry, producing good quality, safety, and customer satisfaction is non-negotiable. One of the most powerful tools used to achieve this is Failure Modes and Effects Analysis (FMEA). The concept of Severity in FMEA is playing an important role. It evaluates the seriousness of a potential failure’s effect on the customer. 

In this article, we’ll explore the meaning of Severity as defined in the AIAG-VDA FMEA standard, understand its role in the 7-step FMEA process, and learn how to apply Severity ratings effectively using real-world automotive examples. 

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What is Severity in FMEA and Why It Matters #

In automotive manufacturing, preventing failure is more cost-effective and safer than correct it in regular mass production. That’s where FMEA (Failure Mode and Effects Analysis) comes in as a structured tool to identify and reduce risk of potential failures.

In FMEA methodology, there is a powerful rating: Severity.

Severity measures the seriousness of the consequences of a failure mode. What consequences occur if the failure happens. It simply asks:

“If this failure happens, how bad will be the impact on the customer, system, or end user?”

The higher the severity, the more risk there is. Even if the occurrence is rare or detection is strong.

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What is Severity in FMEA? (AIAG-VDA Definition) #

According to the AIAG-VDA FMEA Handbook (2019):

“Severity is the consequence of a failure mode on the function as perceived by the customer (internal or external).”

It is a scale from 1 to 10, where:

• 10 = Most Severe (e.g., safety failure or legal non-compliance)
• 1 = Least Severe (e.g., no noticeable impact)

Severity is always given based on the effect only, not the cause.

Where Does Severity Come From in FMEA? #

1. From the Effect of Failure Mode

Severity is always linked to the effect – what happens if the failure mode occurs.

2. From the Function and Requirement

Every FMEA starts with the function (what the system/component/process is supposed to do) and the associated requirement (how well it should do it).

• If the function is safety-critical, any failure will likely result in Severity = 9 or 10.
• If the requirement is linked to legal, regulatory, or customer-specific expectations, the effect of non-compliance increases the severity rating.

3. From the Customer’s Perspective

Severity must be judged from the end user’s or next process customer’s viewpoint:

• How will the failure affect the driver, passenger, or assembly line downstream?
• Will it cause injury, dissatisfaction, recall, or compliance failure?

It is always recommended to get the severity and top level failures from your customer. This will make sure that customer failures into your FMEA. Similarly you can do it with your supplier.

This best practice shows the linkages of FMEAs throughout the supply chain.

4. From the AIAG-VDA Severity Tables

Ultimately, you assign the rating using the standard 1–10 scale provided in the AIAG-VDA Handbook, based on the type of FMEA:

• Use DFMEA table for design-related effects
• Use PFMEA table for process-related effects
• In both, Severity comes from matching the described effect to the most appropriate rating description

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DFMEA Severity Rating Table (AIAG-VDA) #

Rating	Effect	AIAG-VDA Severity Criteria	Description	Example (Automotive)
10	Very high	Affects safe operation of the vehicle and/or other vehicles, the health of driver or passenger(s) or road users or pedestrians.	Involves Safety of end userHazardous – Without warning	Airbag fails to deploy during crash
9	Very high	Noncompliance with regulations.	Involve legal and regulations.Hazardous – With warning	Brake performance reduced, warning light active
8	High	Loss of primary vehicle function	Loss of primary function	Engine fails to start
7	High	Degradation of primary vehicle function	Major degradation	AC cooling drastically reduced
6	Moderate	Loss of secondary vehicle function.	Secondary function failure	Infotainment system doesn’t work
5	Moderate	Degradation of secondary vehicle function.	Comfort/Convenience issue	Power window moves slowly
4	Moderate	Very objectionable appearance, sound, vibration, harshness, or haptics.	Minor issue	Dashboard light flickers
3	Low	Moderately objectionable appearance, sound, vibration, harshness, or haptics.	Appearance issue	Minor scratch on panel
2	Low	Slightly objectionable appearance, sound, vibration, harshness, or haptics.	Very Slight – Nuisance only	Slight rattle in gear knob
1	Very low	No effect	None	Cosmetic defect invisible to user

Rule of Thumb: If Severity ≥ 9, it always need action and special care, regardless of other ratings.

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PFMEA Severity Rating Table (AIAG-VDA) #

Rating	Effect	Impact to Your Plant	Impact to Ship-to plant/ customer	Impact to End User	Example (Automotive)
10	High	Failure may result in health and safety risk for manufacturing worker.	Failure may result in health and safety risk for manufacturing worker.	Affect health of driver or passengers or road users or pedestrians.	Missing weld on seat frame – Seat detaches during crash
9	High	Plant regulatory non-compliance	Plant regulatory non-compliance	Noncompliance with regulations.	Brake fluid underfilled – Braking compromised with dashboard warning
8	Moderately high	100% production may have to be scrapped.	Line shutdown greater than full shift. Stop shipment or field repair or replacement needed	Loss of primary vehicle function	Engine not assembled correctly – Vehicle won’t start
7	Moderately high	Sorting required or less than 100% may have to be scrapped. Deviation or decrease line speed or added manpower.	Line shutdown from 1 hour to full shift.	Degradation of primary vehicle function	Misaligned suspension component – Rough or unstable drive
6	Moderately low	100% of production rework off-line	Line shutdown upto one hour	Loss of secondary vehicle function	Speaker wire not connected – No sound from infotainment
5	Moderately low	Portion of production rework off-line	Possibility for defective product, sorting required, no line shutdown	Degradation of secondary vehicle function	Door rubber seal misaligned – Wind noise at high speed
4	Moderately low	100% of production rework in-station	Defective product triggered major reaction plan, no sorting required	Very objectionable appearance, sound, vibration, harshness, or haptics	Paint overspray on inner panel – Not customer-facing but visible at service
3	Low	Portion of production rework in-station	Defective product triggered minor reaction plan, no sorting required	Moderately objectionable appearance, sound, vibration, harshness, or haptics	Visible dust under clear coat on hood
2	Low	Slight inconvenience to process	No sorting, requires feedback to supplier	Slightly objectionable appearance, sound, vibration, harshness, or haptics	Slight label misalignment on component
1	Very low	No effect	No effect	No effect	Non-visible cosmetic variation inside part enclosure

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Where Severity Fits in the 7-Step FMEA Process #

Severity is determined during Step 4: Failure Analysis of the AIAG-VDA 7-Step Approach:

1. Planning & Preparation (5Ts)
2. Structure Analysis
3. Function Analysis
4. Failure Analysis
5. Risk Analysis  ← 🎯 Severity is rated here
6. Optimization
7. Results Documentation

In this step, teams:

• Assign a Severity rating to identified failure effects
• Followed by Preventive, Detection action and associated occurrence and detection rating.
• Based on all three ratings calculate the Action Priority for respective risks.

Tip: If multiple effects exist, always use the highest Severity.

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Real-World Automotive Severity Examples (DFMEA + PFMEA) #

1st Example – DFMEA: Electric Parking Brake

• Function: Hold the vehicle stationary when parked
• Failure Mode: Brake doesn’t engage
• Effect: Car rolls away on incline
• Severity: 10 – Safety risk, no warning

2nd Example – PFMEA: Seat Assembly

• Process Step: Bolt tightening
• Failure Mode: Bolt under-torqued
• Effect: Seat becomes loose, fails crash test
• Severity: 9 – Safety degradation, with potential warning

3rd Example – PFMEA: Label Printing

• Failure Mode: Label unreadable
• Effect: Loss of traceability
• Severity: 6 – Quality issue, non-safety

Case Study – Seatbelt DFMEA

• Function: Restrain passenger
• Requirement: 10 kN load capacity
• Failure Mode: Webbing tears at 6 kN
• Effect: Passenger unrestrained in crash
• Severity: 10 – Life-threatening

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Common Mistakes in Assigning Severity (and How to Fix Them) #

Mistake	Correction
❌ Assuming rare events = low severity	✅ Severity is independent of occurrence
❌ Using vague terms like “serious problem”	✅ Describe measurable, real-world effects
❌ Using high severity (9-10) for every case	✅ Base it on customer impact, safety, compliance
❌ Not reviewing Severity after design changes	✅ Always re-evaluate after any change
❌ Confusing local vs. end-user effect	✅ Rate based on final effect on customer

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Best Practices for Using Severity in FMEA #

• Use correct severity tables (DFMEA vs PFMEA)
• Involve cross-functional teams – design, quality, safety, manufacturing
• Always justify severity ratings clearly in the FMEA sheet
• Link high Severity to special characteristics (SC, CC, safety)
• Use severity to drive Action Priority (AP) decisions
• Reflect Customer-Specific Requirements (CSRs) in severity evaluations

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Severity Evaluation Checklist (Use in DFMEA / PFMEA) #

• Are all effects clearly defined?
• Are we using the correct severity table (Design or Process)?
• Is the end user and customer’s perspective considered?
• Have we assigned the highest Severity for multiple effects?
• Are ratings traceable and justified with system-level logic? Ex. Have we considered severity from customer.

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Why Severity is Critical in FMEA #

• It is a first step in Risk Evaluation (before Occurrence/Detection)
• It ensures safety and compliance are never ignored
• It aligns design, manufacturing, and quality priorities
• It keeps the focus on preventing customer-impacting issues

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Summary / Key Takeaways #

• Severity = seriousness of effect, not frequency (Occurrence) or detectability (Detection)
• Rated on a 1-10 scale as per AIAG-VDA standard
• if severity ≥ 9 = High Priority based on Action Priority in FMEA, even if Occurrence/Detection are low
• Always consider end-user impact, not just internal consequences
• A correct Severity rating ensures FMEA remains a true preventive tool

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