Why You Shouldn’t Ignore Your Car’s Check Engine Light

It may cost you more in the long run.

You’re driving along and suddenly your check engine light goes on. But nothing seems to have changed with the way your car is running. It’s OK to let it go for a bit, right? Bad idea. The light is an indicator that there’s something wrong with your vehicle. It could mean anything from a loose gas cap to serious engine troubles.

“A check engine light cannot be ignored,” says John Burkhauser, an auto repair specialist and director of educational programs at Bolt On Technology. “The system is telling you that something has failed and will immediately cause damage to your vehicle that will be costly to repair.”

Ignoring your check engine light could result in immediate car problems or deterioration over time. “These codes are annoying, but they can be serious enough to leave you on the side of the road,” says Lauren Fix, The Car Coach. Make sure that doesn’t happen by learning the 14 signs your car is about to die.

Why your check engine light goes on

You may not be seeing any immediate issues with your car, because your car’s internal systems may have the ability to override the cause, Burkhauser says. But it’s not running as well as it should be. “Over time and distance, this problem can become a bigger problem and affect other sensors and systems,” Burkhauser says.

Continuing to ignore the check engine light on can also hide other issues, he notes. Because one light indicates so many different possible failures, other items can fail and be hidden behind the first failure. That can become an issue when the vehicle is looked at to fix the problem.

The mechanic may get a list of codes telling them what systems or sensors have an issue, Burkhauser says. There’s a specific order of diagnosis, because one sensor or system failure can cause another to system to fail. “The tech needs to fix one item first, then diagnose the vehicle to see if the other issues were fixed,” he says.

So why did your check engine light go on in the first place? Here are some common reasons, according to Fix:

  1. Lost or missing gas cap
  2. Bad oxygen sensor
  3. Emission problems
  4. Engine problems

What you can do about a check engine light

Now that you’ve decided not to ignore your check engine light, you can bring your car in to find out the case. Or you can also figure out what’s going on yourself.

Fix recommends you buy a pocket scan tool—they work in cars made in 1996 and later. Called OBD-II or “on-board diagnostics second generation,” the tool will automatically read diagnostic trouble codes. You can get them for about $50 online or in auto parts stores.

“You can plug the scan tool into the OBD II port, a 16-pin connector under the dash,” Fix says. “If you get a code, write it down.” Then check your owner’s manual to see what needs to be repaired. But before you bring your car in for service, find out the 30 things car mechanics won’t tell you.

Jen McCaffery
Jen McCaffery covers money, tech, products, health and safety for Reader's Digest and other publications and websites. When she’s not writing or editing, she’s growing veggies or trying to figure out the way home from assorted trails.