Our sources, in order
- Owner’s manuals and carmaker support pages. What a light means and what to do is the maker’s call, so we quote the manuals, such as Honda’s online owner’s manuals and Ford’s owner support.
- The Federal Motor Vehicle Safety Standards (49 CFR part 571). They set what some warning lights must look like and what color they must be, and when systems such as tire pressure monitoring must warn you.
- Government agencies and industry bodies for their own subjects: the EPA for on-board diagnostics, the U.S. Tire Manufacturers Association and tire makers for tire care.
When manuals differ
Carmakers don’t always agree, and the same light can mean slightly different things in different cars. When that happens we show each source rather than pick one, and say so. Your own manual is the final word for your car.
Our drawings
The warning light symbols and diagrams are drawn by us, after the shapes in the federal standard. We don’t copy carmakers’ artwork or manual pages.
Checking and updating
Each page shows the date it was last updated and lists its sources at the end. If something doesn’t match your manual, let us know.