# Sources and methods

## Where the data comes from

| Pages | Source |
| --- | --- |
| Trouble codes | Generic code definitions from SAE J2012; causes, checks and fixes written by our editors from service practice |
| Warning lights and symptoms | Written by our editors; safety guidance follows NHTSA and the vehicle makers' owner's manuals |
| Repair costs | Typical parts prices plus labor at the 2026 US independent-shop rate ($110-$190 an hour) and standard labor times |
| Tire tools | Pure math from the size code; load index and speed rating tables from the tire industry standards (ETRTO/ISO) |
| Makes, lineups and model specs | The US DOE/EPA fueleconomy.gov vehicle dataset (models, size classes, engines, transmissions, drivetrains, mpg, EV range), refreshed with scripts/import-epa.mjs. Heavy-duty pickups, which have no EPA label, are listed by hand |

## Reference sources we cite

- [EPA: On-Board Diagnostics (OBD)](https://www.epa.gov/state-and-local-transportation/vehicle-emissions-board-diagnostics-obd)
- [SAE J2012: Diagnostic Trouble Code Definitions](https://www.sae.org/standards/content/j2012_201812/)
- [NHTSA: Check for recalls by VIN](https://www.nhtsa.gov/recalls)
- [NHTSA: Tires](https://www.nhtsa.gov/equipment/tires)
- [NHTSA: Tire pressure monitoring systems](https://www.nhtsa.gov/equipment/tires#tire-pressure)
- [NHTSA: Air bags](https://www.nhtsa.gov/equipment/air-bags)
- [NHTSA vPIC: Vehicle product information catalog](https://vpic.nhtsa.dot.gov/)
- [fueleconomy.gov (US DOE and EPA)](https://www.fueleconomy.gov/)
- [fueleconomy.gov: Keeping your vehicle in shape](https://www.fueleconomy.gov/feg/maintain.jsp)
- [ASE: National Institute for Automotive Service Excellence](https://www.ase.com/)
- [Car Care Council: Car care guide](https://www.carcare.org/car-care-guide/)
- [Battery Council International](https://batterycouncil.org/)
- [U.S. Tire Manufacturers Association: Tire care](https://www.ustires.org/tire-care)
- [AAA: Approved Auto Repair](https://www.aaa.com/autorepair/)
- [NHTSA: Vehicle safety complaints and recalls (api.nhtsa.gov)](https://www.nhtsa.gov/nhtsa-datasets-and-apis)

## How we handle mistakes

Every page has a "Report a mistake" link. We check each report against the source and update the page; the "Updated" date at the bottom of each page shows when it last changed.

## Prices

Costs are typical ranges, not quotes. Your price depends on the vehicle, the parts brand, your region and the shop. Get a written estimate that splits parts and labor before agreeing to a repair.

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Source page: https://diagxcar.com/sources
General information, not a substitute for a qualified mechanic.