Downtime reason codes are a standardized set of short labels that describe why a machine stopped — for example BRK for a breakdown or SET for a changeover. They turn raw stoppage time into structured data you can analyze, so you can see which causes actually drive your losses instead of guessing. This guide gives you a ready-to-use reason-code list, shows how to map each code to OEE and the Six Big Losses, and explains how to roll codes out on the shop floor. To start tracking today, use our OEE calculator and the free downtime template linked below.
What are manufacturing downtime reason codes?
A downtime reason code is a controlled category assigned to every production stoppage. Instead of an operator writing a free-text note like “machine broke,” they select a fixed code (and optionally a sub-reason). Because every stop is classified the same way, the data can be summed, ranked and compared across shifts, machines and plants. Reason codes are the difference between knowing you lost 8 hours last week and knowing that 5 of those hours were changeovers on Line 2.
The standard downtime reason-code list
The list below is a proven starting point used across 450+ TeepTrak deployments. Keep the number of top-level codes small (15–20) so operators can select the right one in seconds; add sub-reasons only where they change the action you would take.
| Code | Reason | OEE factor | Six Big Loss | Counts as a loss? |
|---|---|---|---|---|
| BRK | Breakdown / equipment failure | Availability | 1. Breakdowns | Yes |
| SET | Setup / changeover | Availability | 2. Setup & Adjustments | Yes |
| ADJ | Adjustment / settings | Availability | 2. Setup & Adjustments | Yes |
| TOOL | Tooling change or failure | Availability | 2. Setup & Adjustments | Yes |
| NOM | No material / starvation | Availability | 1. Breakdowns | Yes |
| NOP | No operator / no labour | Availability | 1. Breakdowns | Yes |
| BLK | Blocked / downstream full | Availability | 1. Breakdowns | Yes |
| MIN | Minor stop / jam / misfeed | Performance | 3. Idling & Minor Stops | Yes |
| CLN | In-process cleaning | Performance | 3. Idling & Minor Stops | Yes |
| SPD | Reduced speed / slow cycle | Performance | 4. Reduced Speed | Yes |
| QDF | Quality defect / scrap | Quality | 5. Process Defects | Yes |
| REW | Rework | Quality | 5. Process Defects | Yes |
| STU | Startup reject / warm-up scrap | Quality | 6. Startup Rejects | Yes |
| PM | Planned maintenance | Planned | n/a | No (excluded) |
| BRK-PL | Planned break / lunch | Planned | n/a | No (excluded) |
| MTG | Meeting / training | Planned | n/a | No (excluded) |
| NOD | No demand / not scheduled | Planned | n/a | No (excluded) |
Get the free Downtime Tracking Sheet (Excel)
Log every stop by reason code with standardized codes and an automatic Pareto of your biggest losses.
How downtime reason codes map to OEE and the Six Big Losses
Every reason code should roll up to one OEE factor. Availability losses are unplanned stops (breakdowns, changeovers, starvation). Performance losses are minor stops and reduced speed. Quality losses are defects and startup rejects. Planned activities (maintenance, breaks, no demand) sit outside the OEE calculation entirely. This mapping is what lets a single downtime log feed your OEE, your Pareto of causes, and your improvement plan at the same time.
How to structure and roll out reason codes
Keep the top level short and unambiguous, name codes in the operator’s language, and make “one stop = one code” the rule. Review the Pareto monthly: if a catch-all code like MIN dominates, split it into sub-reasons so the data points to a specific fix. Avoid an “Other” code becoming a dumping ground — if “Other” is in your top three, your list is missing a real category.
FAQ
What are downtime reason codes?
Downtime reason codes are standardized labels that classify why a machine stopped, such as breakdown, changeover or minor stop. They convert unstructured stoppage notes into consistent data that can be summed and ranked to find the biggest causes of lost production.
What is a good set of downtime reason codes?
A good set has 15–20 clear top-level codes, each mapped to one OEE factor (Availability, Performance or Quality) or marked as planned time. Operators should be able to pick the right code in seconds, with sub-reasons added only where they change the corrective action.
How do reason codes relate to OEE?
Each reason code rolls up to one OEE factor: breakdowns and changeovers reduce Availability, minor stops and slow cycles reduce Performance, and defects reduce Quality. Planned activities like maintenance and breaks are excluded from OEE. This mapping lets one downtime log drive both your OEE and your Pareto of loss causes.
Should planned downtime have reason codes?
Yes — track planned maintenance, breaks and no-demand with their own codes, but flag them as excluded from OEE. Recording them keeps your Availability denominator honest and shows how much calendar time is scheduled versus truly lost.
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