Starting with 1996 model-year vehicles, automakers standardized all onboard computers under a system called OBD II (Onboard Computer Diagnostic). This system instituted a list of diagnostic trouble codes and mandated that all cars provide a universal connector to access this data.

These trouble codes – a series of numbers/letters – is the diagnostic “language” that detects the source of the problem. There are literally hundreds of these trouble codes, each one with the ability to trigger your check engine light. Reasons for an illuminated check engine light range from emissions control issues and transmission problems to a loose gas cap.

If one of these computer codes triggers your check engine light, you can do two things:

1. Diagnose the problem yourself by buying an OBD II scanner and checking the engine codes yourself. (It’s pretty easy.)
2. Take your car to a certified professional for a proper diagnosis

Whatever choice works best for you, keep in mind that the trouble code will only point to the system that’s having the problem. It won’t tell you how or why to fix it. But it is a good starting point.

Simply put, an engine diagnostic test can reveal any issues or problems you may be having with your car. Everything from your engine, transmission and exhaust system to brakes, coolant and performance issues.

Thanks to the computerization of cars, with their microchips, sensors and processors, diagnostic testing is no longer expensive and time-consuming. Specialized software can quickly point to a problem area anywhere in your car.

Some drivers even take their cars in for routine diagnostic testing. A regularly scheduled diagnostic test can uncover a minor problem before it turns into a major problem, even before it triggers the check engine light. (By the way, diagnostic testing comes in handy when you’re checking out a used car.)

If your check engine light is flashing, you need to pull over immediately and turn off your car, especially if accompanied by oil or temperature warning lights.

A flashing check engine light spells trouble. If you continue to drive you’ll risk serious – and expensive — damage to your engine.

However, a flashing light is different than a check engine light that is simply illuminated. Not every check engine warning light signals a parade of big bills. Sometimes the problem is as simple as tightening the fuel cap.

Every responsible driver should understand the meaning of their car’s warning lights. The owner’s manual will help explain these symbols and show where they’ll appear on the dash. The lesson here is don’t ignore any warning light that comes on.

And no, placing a piece of black electrical tape over the light will not make the issue go away. For more information, see our article What Happens When I Get a Check Engine Warning?

There are many reasons why your check engine light comes on, but not all of them are serious. For example, one of the more common reasons for the light to come on is a faulty gas cap. It might need replacing or it could simply be loose.

Sometimes a check engine light will come on when nothing is really wrong with your car. A change in humidity or other temporary changes in the environment could trigger the light. If that’s the case, the light will go off by itself after a relatively short period of driving time.

However, an illuminated check engine light could also be a huge red flag being waved right in front of your face warning you of a more serious problem. Are you releasing excess pollutants? Are you consuming too much fuel? You just never know. (By the way, if your check engine light is flashing, pull over immediately and turn off the car. A flashing light spells trouble.)

In short, if your check engine light comes on, you have two options:

1. You can diagnose the problem yourself by buying an OBD II scanner and check the engine codes.
2. If you’re not the DIY type, and most drivers aren’t, take your car to a mechanic and let the experts do their job.

That’s the million-dollar question. If your check engine light comes on and stays on, there are two things you can do:

1. Diagnose the problem yourself by buying an OBD II scanner and checking the engine codes.
2. Take your car to a certified professional for a proper diagnosis.

Some drivers feel confident working on their own cars. If so, option #1 may work. But for the majority of drivers, we recommend taking the car to a professional mechanic. The issue could be anything from a loose gas cap to something more serious, like a misfiring engine. You just never know.

Here’s something else to consider: Are other warning lights coming on as well, like temperature or oil pressure? If so, then you’re dealing with a major problem and your car needs service without delay.

One more thing, and we can’t stress this enough — if your check engine light is flashing, pull over immediately and stop your car. Not kidding. There’s something majorly wrong and you don’t want to risk further damage by driving it.

In the end, if your check engine light comes on, it’s best to heed the age-old advice…it’s better to be safe than sorry.