Low fuel light
A fuel pump shape, amber
Nothing is wrong · Amber means get it checked
Low Fuel Light
Get to a gas station when you can. This isn't a light that needs a shop visit — it means exactly what it looks like.
What the light means
Your car has detected that the fuel level in the tank is low, usually somewhere around the last eighth to a tenth of a tank, depending on the vehicle. It's a straightforward warning: fill up soon.
Why it comes on
There's really only one cause here. Unlike most warning lights, this one doesn't have a list of possible problems behind it. It comes on because the fuel level sensor in the tank has read low fuel, and it's telling you before you run out.
The only wrinkle worth knowing is that fuel gauges are not perfectly precise. How many miles you actually have left when the light comes on varies by car, by how you're driving, and even by how level the ground is. Treat the light as a warning to fill up soon, not a countdown you can time exactly.
The less obvious part
Running the tank very low on a regular basis is worth avoiding for a reason that has nothing to do with running out of gas. In most cars, the fuel pump sits inside the tank, and the fuel around it is what keeps it cool while it runs. When the tank is low, the pump can end up running hotter than it should, especially in stop-and-go driving or in hot weather. Do that often enough over the life of the car and it can shorten the pump's life. This isn't something to worry about after one or two low tanks. It's a habit thing, not a one-time risk. If you're the kind of driver who often lets it get down toward empty, filling up a bit earlier is cheap insurance. Fuel pump replacement, if it ever comes to that, is a bigger job than a fill-up.
What to do about it
Fill the tank. There's no repair needed and nothing to diagnose. If the light comes on and the gauge itself seems to be reading incorrectly — for instance, if it says full right after you've filled up, or it never seems to move — that's a different issue, and worth having someone look at the fuel level sensor or gauge wiring. But that's a separate problem from the light doing its normal job.