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.

Service Reminders

Some auto companies use mileage or time as a good system for reminding you to take your vehicle in on a regular schedule. But some cars have a built-in system that is a part of a vehicle’s engine control unit that can track a range of things related to engine performance, and will know when it’s time for servicing. Sometimes the engine light switches on because all you need is to visit an oil change business for a change. And sometimes it’s just telling you that the car’s not running as well or as efficiently as it could, and that it needs to be taken to an oil change business for servicing.

Safety Components

There are several other systems that monitor the safety mechanisms that are built into the car. They can be pretty complex, but there are generally two things that are most common when it comes to triggering the check engine light.

The engine light may mean that there’s something wrong with the brake system. Brakes are in constant use and they tend to wear out over time. Some cars will let you know when those brake pads are getting ground down a little too much and it’s time for a new set of pads that may be available at an oil change business.

The other important safety system that can be behind the engine light is the transmissions system. Once called the gearbox, the transmission is closely related to the engine but often has its own computerized monitoring system. Any problem along the sensors could set off the engine light.

Those are the most common problems that can cause the engine light to switch on. But that’s a lot of problems. How are you going to know what the problem is? Even if you know a thing or two about cars, it can still be time consuming. The best and safest way to deal with the engine light is to take it into an oil change business… after you try tightening the gas cap that is.