Engineering change: ECR, ECN and PCN explained
The difference between an ECR, ECN and PCN, what an engineering change notice contains, and how a controlled change flows from request through review to updated documents.
Products change. A tolerance is opened up, a component is superseded, a supplier is switched, and every change is a chance for a product’s documentation to fall out of step with reality. Change control is the discipline that keeps them aligned. It runs on a small family of documents whose acronyms are easy to confuse: the ECR, the ECN, and the PCN. This guide explains each and how a controlled change actually flows.
ECR, ECN and PCN
The three documents mark different points in a change:
| Document | What it is |
|---|---|
| ECR: Engineering Change Request | A proposal to change something, with the reason and justification |
| ECN: Engineering Change Notice | The approved instruction that authorizes and defines the change |
| PCN: Product / Process Change Notification | A notice to customers that a change has been or will be made |
In short: an ECR asks, an ECN orders, and a PCN informs. Not every change needs all three (an internal tweak may never generate a PCN), but in regulated or customer-driven supply chains, a change that affects form, fit, function, or a customer’s approved configuration usually does.
What an engineering change notice contains
- A unique change number, the affected part(s) and the revision before and after
- A clear description of the change and the reason for it
- The disposition of existing stock and work in progress (use, rework, scrap)
- The effective date or the point of cut-in
- The documents affected: drawing, BOM, routing, control plan, work instructions
- The approvals required, and the record that they were obtained
The most valuable field on an ECN is the list of affected documents. A change that updates the drawing but not the work instruction or the control plan is how a “completed” change quietly reintroduces the old part.
How a controlled change flows
A change moves through a defined path: a request (ECR) is raised, a change control board or reviewer assesses impact and cost, and if approved, an ECN authorizes it. Implementation then ripples into every affected document, and where a customer’s approved product is touched, a PCN goes out and a fresh PPAP submission or an updated Declaration of Conformity may be required. The point of the process is traceability: being able to show what changed, why, who approved it, and when it took effect.
Change control as a documentation discipline
Change control is fundamentally about keeping a set of documents consistent as they evolve, which is far easier when those documents live in a controlled, version-controlled structure rather than as scattered files. Holding documents in a system where revisions and history are explicit is the same standardization discipline that keeps product documentation consistent in the first place. DataSheets Pro provides a structured starting point with version history; defining your change process and approvals remains your responsibility.
Start from the templateEngineering Change Request template: free & editable
Propose a change (the problem, the affected items and the justification) and route it for review, then export a print-ready ECR as a PDF, free to start.
Open the template →Standardize this in DataSheets Pro
Turn what you just read into a repeatable, on-brand template, with no design tools required.