That's not to be taken lightly. It can mean something is amiss with your engine's operating systems, including the crankshaft sensor, mass airflow sensor and coolant sensor, which tells you the temperature of the engine.
"All these send the information to the computer and it relates it to the engine and fuel economy," said Leon Kaplan, "The Motorman."
Kaplan has been around engines his entire life. His shop, like others, has had to adapt to modern computer engine systems. He diagnoses cars for customers on a regular basis. You can also check into it yourself.
"For consumers to understand that, they need a conduit to get that type of information. CarMD is that conduit," said CarMD spokesman Art Jacobsen.
The CarMD, which costs $120, simply plugs into the standard connector on any modern car. It'll then read codes stored by something not working right - codes that activate the "check engine" light.
"Find out what's going on so you can understand what's the most cost-effective way for you to take care of that vehicle and save yourself money in the long run," said Jacobsen.
But home mechanics should be careful to not just start replacing parts. A component can activate the light but still be OK.
"It could mean something in that area that's causing something the problem - maybe a broken wire, maybe it just became disconnected. It's a plug-in system, so maybe it just disconnected. It could be that simple," said Kaplan.
So let's say you're able to check or take your car to a mechanic and find out that the "check engine" light is just for something minor and it's not affecting your gas mileage. Well, you still don't want to let it go, because that could be a problem every two years.
When you go in for a smog check to renew your plates, a "check engine" light being on is an automatic fail.
If something isn't right, your car can tell you these days. Don't ignore the warning sign. It's not just an annoyance, it means you could be wasting lots of fuel.
"Don't neglect it. You're only wasting money, and you're actually hurting your automobile," said Kaplan.