PPAP rejections cost automotive suppliers time, money, and customer confidence. Most rejections are avoidable — they trace to misunderstood requirements and incomplete packages.
PPAP (Production Part Approval Process) requires automotive suppliers to complete 18 documented elements — from design records and PFMEA to dimensional results and Cpk studies — and submit them at one of five levels to prove their production process consistently produces conforming parts. Level 3 (full package submission) is the default; a Cpk below 1.67 on critical characteristics is the single most common rejection reason. PPAP is defined in the AIAG PPAP manual (4th edition) and required under IATF 16949 Clause 8.3.4.4.
PPAP was developed by the Automotive Industry Action Group (AIAG) as a standardized method for automotive suppliers to demonstrate that their production processes can consistently produce parts that meet customer engineering and quality requirements. The core question PPAP answers: before we commit to full-rate delivery of this part, can you prove that your production process — not a prototype, not a sample made by engineering — actually produces conforming output?
PPAP matters because the cost of discovering a process problem during full production is orders of magnitude higher than discovering it before first delivery. A PPAP requirement creates a structured gate where evidence of process capability must be provided before the customer accepts delivery. Most major automotive OEMs have customer-specific requirements that augment the base PPAP manual — the AIAG manual is the floor, not the ceiling.
One of the most commonly misunderstood aspects of PPAP is the submission level. Not every PPAP requires submitting all 18 elements to the customer. The submission level determines what must be sent to the customer versus what must be retained at the supplier's facility.
Level 1: Part Submission Warrant (PSW) only. The customer receives only the warrant. All supporting elements are retained at the supplier. Used for bulk materials and minor design changes by agreement.
Level 2: PSW with product samples and limited supporting data. The customer receives the warrant plus selected supporting documentation and physical samples.
Level 3: PSW with product samples and complete supporting data. This is the default submission level for most initial PPAPs. The customer receives the full package.
Level 4: PSW and other requirements as defined by the customer. Used for non-standard submissions where the customer specifies exactly what is required.
Level 5: PSW with product samples and complete supporting data — reviewed at the supplier's facility. The customer reviews the package on-site rather than receiving it. Used for complex parts or when the customer wants to observe the process.
The submission level is specified in the purchase order or customer-specific requirements. If not specified, Level 3 is the safe assumption. When in doubt, ask before submitting — a Level 1 submission when the customer expected Level 3 will be rejected and requires resubmission.
1. Design Records. The current design documentation for the part — drawings, specifications, math data (CAD files), and all referenced design documents. Must reflect the current engineering revision.
2. Authorized Engineering Change Documents. Any approved but not yet formally incorporated engineering changes that apply to the part. These must be documented and the PPAP submission must reflect their requirements.
3. Customer Engineering Approval. For any deviation from a drawing requirement, formal customer engineering approval is required before PPAP submission. Without this, out-of-tolerance characteristics on the part submission warrant are rejections.
4. Design Failure Mode and Effects Analysis (DFMEA). If the supplier has design responsibility (design-responsible supplier), the DFMEA is required. If the customer holds design responsibility, this element is N/A for the supplier. The DFMEA must reflect current design risk and show evidence of review and update.
5. Process Flow Diagram. A flow chart showing the entire manufacturing process from receipt of incoming materials through final packaging and shipment. Every step that affects part quality — including special processes, inspection points, and material handling steps — must be shown. The flow must match the actual process sequence.
6. Process Failure Mode and Effects Analysis (PFMEA). An analysis of every manufacturing process step for potential failure modes, their effects, current controls, and risk priority numbers (RPNs). The PFMEA is linked to the process flow diagram: every process step in the flow should appear in the PFMEA.
High-RPN items in the PFMEA should drive the control plan. Auditors look for consistency between the PFMEA severity, occurrence, and detection ratings and the controls documented in the control plan.
7. Control Plan. The roadmap for controlling production quality from incoming material through outgoing final inspection. The control plan lists every controlled characteristic, the control method, the sample size and frequency, and the reaction plan when out-of-control conditions occur.
The control plan must be aligned with the PFMEA: characteristics identified as high risk in the PFMEA should have robust controls in the control plan. Auditors look for gaps — high-RPN failure modes with no corresponding control.
8. Measurement System Analysis (MSA). Statistical evidence that the measurement systems used to measure controlled characteristics are adequate — that measurement error is a small fraction of the part tolerance.
For variable data, Gauge R&R (Repeatability and Reproducibility) studies are required. Acceptable Gauge R&R results are typically under 10 percent of tolerance (acceptable), 10 to 30 percent (marginally acceptable, improvement required), and over 30 percent (unacceptable — do not use this gauge for production inspection until improved).
Attribute gauges (go/no-go) require attribute agreement analysis with multiple appraisers.
9. Dimensional Results. Measurement results for all controlled characteristics on a production-representative part. Unlike a general dimensional inspection, PPAP dimensional results must be from a part made using the intended production tools, production process, and production operators. Prototype measurements do not satisfy this requirement.
Every characteristic on the drawing must appear in the dimensional results, with the nominal, tolerance, and actual value recorded. The part must be identified — serial or lot number — to provide traceability.
10. Records of Material / Performance Test Results. Test results confirming that the part meets all material and functional requirements. Material test results confirm that the raw material meets its specification. Performance test results confirm that the part meets all functional requirements — strength, fatigue, corrosion resistance, dimensional stability under load, or any other engineering test requirement specified on the drawing or in referenced specifications.
11. Initial Process Study. Statistical evidence that the manufacturing process is capable of producing conforming output at production rates. For variable characteristics, Cpk and Ppk calculations are required. Minimum acceptable initial Cpk is typically 1.67 for all critical characteristics.
Initial process study data should be based on a meaningful sample size — AIAG guidance typically recommends 30 or more consecutive parts from a production run. Cherry-picked samples or small sample sizes are not acceptable.
12. Qualified Laboratory Documentation. Evidence that any laboratory used for testing — internal or external — is qualified to perform the tests. Accredited external labs should provide their accreditation certificate. Internal labs should have documented evidence of method validation and auditor approval.
13. Appearance Approval Report (AAR). For parts with appearance requirements — color, texture, gloss, grain pattern — a completed AAR signed by the customer's authorized appearance representative. The AAR requires customer review of physical boundary samples compared to the appearance specification. Most mechanical suppliers can mark this N/A.
14. Sample Production Parts. Physical samples of the part from the PPAP production run, submitted to the customer in the quantity specified. Sample parts should be clearly identified with the part number, revision, and lot or serial number.
15. Master Sample. A production sample retained by the supplier as the reference standard against which subsequent production parts are compared. The master sample is signed and dated by the customer or authorized supplier representative and retained until superseded by a new PPAP.
16. Checking Aids. Any fixtures, gauges, or inspection tools used specifically for this part. Checking aids should be documented, identified, and calibrated. Their performance should be validated in the MSA study.
17. Customer-Specific Requirements. Any requirements from the customer's customer-specific requirements (CSRs) that are not covered by the base PPAP manual. OEM-specific forms, additional analyses, and supplemental data requirements are documented here.
18. Part Submission Warrant (PSW). The summary document that certifies the supplier's declaration that the part and process meet all requirements. The PSW identifies the part, the drawing revision, the submission level, the reason for submission, and includes statements about material compliance (IMDS for automotive), dimensional conformance, and production process readiness.
The PSW must be signed by an authorized representative of the supplier. A PSW signed by someone without authority to certify the submission is a rejection.
Incomplete or mismatched documents. The PFMEA does not include steps shown on the process flow. The control plan lists characteristics not on the drawing. The dimensional results reference a different drawing revision than the PSW.
Cpk below threshold on critical characteristics. Initial process capability below 1.67 on characteristics designated as significant or critical by the customer. Customers will not accept parts with demonstrated insufficient capability — the submission must include a corrective action plan with timeline for achieving the capability target before re-submission.
Gauge R&R results exceeding 30 percent. Measurement system inadequacy that means the supplier cannot reliably detect conforming from nonconforming parts. Must be resolved before the dimensional results are valid.
Missing customer-specific requirements. OEM-specific PPAP requirements not addressed. BMW, Toyota, GM, Ford, Stellantis, and other OEMs all have specific additional requirements beyond the AIAG manual.
PSW signed before all elements complete. The Part Submission Warrant certifies that all elements are complete and conforming. Signing the PSW while elements are still outstanding is a misrepresentation.
Coplain helps automotive suppliers build complete, accurate PPAP packages by generating aligned process flow diagrams, control plans, and work instructions from your existing documentation. Try it free at coplain.com.
Q: What is PPAP and why is it required?
A: PPAP (Production Part Approval Process) is the automotive industry's standard for demonstrating that a supplier's production process consistently produces parts meeting customer requirements before full-rate delivery begins. It is defined in the AIAG PPAP manual (4th edition) and required under IATF 16949 Clause 8.3.4.4. Most automotive OEMs additionally specify PPAP in their customer-specific requirements.
Q: What is the default PPAP submission level?
A: Level 3 is the default for most initial PPAPs — the supplier submits the Part Submission Warrant (PSW), product samples, and complete supporting data to the customer. The submission level is specified in the purchase order or customer-specific requirements; if not specified, Level 3 is the safe assumption.
Q: What is a Part Submission Warrant (PSW)?
A: The PSW is the summary document that certifies the supplier's declaration that the part and process meet all engineering and quality requirements. It must be signed by an authorized representative of the supplier. A PSW cannot be signed until all applicable PPAP elements are complete and conforming — signing before then is a misrepresentation of the submission status.
Q: What Cpk is required for PPAP approval?
A: Most automotive customers require a minimum Cpk of 1.67 for safety and critical characteristics, and 1.33 for standard characteristics, measured on the initial process study (typically 30+ consecutive production parts). Cpk below these thresholds requires either engineering disposition or a corrective action plan with a timeline for achieving the required capability before the PPAP can be approved.
Q: When does a new PPAP need to be submitted?
A: A new PPAP (or partial PPAP for the changed elements) is required for: new part or new design, engineering changes, process changes, tooling changes, production location changes, lapse in production (typically 12 months, per customer-specific requirements), and when the customer specifically requests resubmission.
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