Check engine light

If the light is flashing, stop driving and get the car looked at right away, or have it towed in. If it's steady and not flashing, you can drive it carefully for a few days, but don't ignore it. Try to avoid hard acceleration or towing anything until it's checked.

What the light means

The check engine light means the car's computer has detected something outside normal range in the engine or emissions system. It doesn't tell you what, only that something needs a look. A steady light usually means the problem is being monitored but isn't causing immediate harm. A flashing light means the engine is misfiring badly enough that unburned fuel is reaching the catalytic converter, which can damage it fast. That's the difference that matters.

Common causes

The most common cause, by a wide margin, is a loose or failing gas cap or a small leak in the evaporative emissions system. After that, worn spark plugs or ignition coils, a failing oxygen sensor, or a dirty mass airflow sensor are typical. Flashing lights almost always point to a misfire, often from a bad spark plug, coil, or fuel injector. Less often it's something more involved, like a failing catalytic converter or an issue with the fuel system itself.

What it takes to fix

The only way to know for sure is to plug in a scan tool and read the stored codes, then check which ones actually match the symptoms, since more than one code can show up at once. For a steady light, that's usually a straightforward diagnostic that points to one part. For a flashing light, the priority is finding and stopping the misfire before it does more damage to the converter, which is a more expensive part to replace than the ones that usually cause the misfire in the first place.

We can run the diagnostic and tell you what the codes mean and what we'd recommend before doing any work. If it turns out to be something minor, like a loose gas cap, we'll tell you that too.

Warning-light symbols and meanings vary by vehicle — always check your owner’s manual. This is general guidance based on what the light indicates, not a physical inspection, and a light on its own never names a failed part.