If you’ve driven a car that’s been built in the last 15 years, then you’ve probably noticed the check engine light. On most cars, it’s a tiny light on the dashboard that displays the silhouette of an engine. And if you’re like most people, you’ve probably seen it light up at some point while you’re driving.

But what does the light mean? The light usually only says “check engine soon” or “service engine soon”, and that’s pretty vague. So what’s the next course of action when that little light invariably lights up? Usually, you can have the employees at an oil change business look at the light—they may be able to help.

But first of all, let’s talk about the purpose of the engine light. It’s there as an alert to a range of potential problems that an oil change business may be able to handle. The light is the indicator of a system that overlooks a bunch of aspects that keep a car running smoothly. Some include the emissions system, the power train system, and the fuel injection system. And on some models, the check engine light may also be monitoring things like tire pressure, suspension systems, and even the electronics systems that help keep an automobile running smoothly.

So what do those have to do with the engine? After all, the light is in the shape of an engine. But the first thing to remember is that the problem isn’t always under the hood. That could be good news, since the common non-engine troubles are often easier to fix at an oil change business than something engine-related. Electronic systems were first added to engines in the 1970’s, but it wasn’t until the 1980’s that system monitors were implemented. In most cases, those new systems, which were minor, were simply latched onto the main monitoring system, the one that flicks on the engine light. And it’s been the same ever since.

So what does the light mean then? There are three main categories where your car could be experiencing problems:
1. The emissions system
2. Your car has just passed some pre-set amount of time for servicing.
3. A component that affects the safe operation of a vehicle is out-of-whack.

Emissions System
The emissions system is one of the most complicated parts of an automobile. There are several little-known things like the exhaust gas recirculation valve, positive crankcase ventilation system, air pump, charcoal canister, catalytic converter, oxygen sensor, and muffler.

If you’re a normal driver visiting an oil change business, most of these systems are completely foreign to you. But that’s ok, most of the time. These days those things are monitored by advanced and precise electronic systems. But when any of these systems find something wrong, then the light goes on.

Nowadays gas caps are air tight in order to keep fuel from evaporating. And most cars have sensors that can detect a gas cap that’s not attached. This is the easiest problem to fix when the engine light goes on, and thus should be the first thing to check. Sometimes just tightening the cap is enough to get the light to shut off, so check that before you take the time to head over to an oil change business.